FANFARE AS DISNEY OPENS PARK

It may be some time before Wall Street echoes the trumpet fanfares that heralded today's opening of Walt Disney's futuristic addition to the Disney World complex in Lake Buena Vista, Fla.

The $900 million Epcot Center, a melange of advanced technology, science, history and Disney-brand entertainment, opens at a time when Walt Disney Productions is struggling to halt a slide in corporate earnings and a decline in attendance at its well-known parks.

Simultaneously, the company is attempting to revive its slumping movie division and enter the crowded field of pay-television programming.

With Epcot, the late Walt Disney's acronym for Experimental Prototype Community of Tomorrow, Disney appears to have staked its future more than ever on amusement parks, which accounted for 69 percent of revenue in 1981. Epcot is Disney's biggest addition since Walt Disney World opened 11 years ago.

Dependence on New Ventures

Renewed growth by Disney depends on the success of the new ventures, but it may take a year or more before the company's prospects become clear. Nevertheless, some analysts are pleased with what they regard as Disney's direction.

''After stagnating for five years, the company is in the process of becoming a major factor in entertainment again,'' said Alan Kassan, a vice president of the First Manhattan Company.

For the nine months through June 30, Disney's profits fell 14 percent, to $72 million, or $2.17 a share, from $83.8 million, or $2.57 a share, in the similar period a year earlier. Revenue rose 6 percent, to $735.2 million.

Disney is expected to finish its 1982 fiscal year, which ended today, with about $3.15 in earnings per share, versus $3.72 last year. The range of Wall Street forecasts for 1983 is between $4.25 and $5.

The jump is expected to come partly from a rebound in attendance generated by the Epcot opening, plus the opening of a new Disneyland in Tokyo. Disney has no equity in the $450 million Tokyo project, the first of its kind outside the United States, but will be paid a licensing fee of 7.5 percent of the park's revenues.

Attendance this year at Disney World, the country's most popular vacation resort, was down by 5 percent through June, and was not expected to equal last year's total of about 12 million when the count for the 1982 fiscal year stopped on Thursday. Its West Coast counterpart, the 27-year-old Disneyland, in Anaheim, Calif., south of Los Angeles, has been running about 7 percent below the 1981 pace through the summer.

E. Cardon Walker, Disney's chairman and chief executive, said he expects Epcot to bring an additional 8 million people a year through Disney World's turnstiles, raising the total there to more than 20 million. Lagging Movie Division

Although the drop in attendance is a nagging problem, Disney's movie business has been a calamity. Pretax profits in films fell 29 percent through the first three quarters on a 7 percent increase in revenue.

''Families don't go to the movies like they used to, and we just haven't done well,'' Mr. Walker conceded. ''But we're not going to quit trying.''

A recent attempt, ''Tron,'' the story of a man trapped inside a video game and condemned to play until death, did lure some teen-age moviegoers. Its computer-generated images stirred a spate of publicity last spring, but the film drew mixed critical reviews and was a box-office disappointment. Still, the film, which cost $21 million, or more than double the average production cost in Hollywood, is expected to make some money by the time its foreign run is completed.

More important, many considered the new elements in ''Tron'' as evidence that Disney executives have begun to shed their rigid loyalty to Walt Disney's concepts of how to run the business. Mr. Disney died in 1966. Disney's top management has long been branded by industry analysts as insular and overly conservative. Walker Retirement Indicated

Mr. Walker, 67 years old, has been chief executive since 1971 and chairman since 1980. He has indicated that he will retire next spring after the opening of the Tokyo Disneyland, and the start of the Disney Channel on pay television.

Analysts expect that Ronald W. Miller, 49, president and heirapparent, is not likely to quickly change the company's direction. Nevertheless, it was Mr. Miller who opened Disney studios to outside talent and some analysts said he is more willing to consider new approaches.

He said in an interview that the futuristic setting of the vast Epcot Center ''will be a platform'' for hundreds of hours of Disney programming, mainly for the Disney Channel, but also for Disney's weekly program on the CBS television network.

''I think the Disney Channel could be the most rewarding project we have going,'' Mr. Miller said. ''Most of our new programming will be coming out of here and Walt Disney World. If that catches on, a lot of families will be signing up.'' Westinghouse Quits Project

Cable operators are reportedly eager to add the Disney Channel to their offerings when it begins next April. But the Westinghouse Corporation, which was to have been an equal partner, abandoned the effort earlier this month in a programming dispute.

Analysts are divided about the channel's prospects. Skeptics doubt that enough families will pay the monthly $10 fee to receive it. ''I think it will be a fiasco,'' said Arthur E. Rockwell, an analyst with Crowell, Weedon & Company, in Los Angeles.

Still, Disney expects to draw two million subscribers by next spring. ''It's a good concept,'' said Harold Vogel of Merrill Lynch, ''and it should be a nice contributor to earnings in six to eight years.''

Epcot, on the other hand, is expected to enhance Disney's profitability almost immediately. The company's $600 million initial investment in the project, in real terms, is less than half the $700 million it took to open Disney World in 1971.

In addition to the $600 million of its own money, Disney received another $300 million from sponsors such as the Exxon Corporation, the General Motors Corporation, the Eastman Kodak Company and the American Telephone and Telegraph Company.

At today's closing price of $57.125 on the New York Stock Exchange, a gain of 50 cents, Disney's market value is about $2 billion. At that price, Mr. Kassan argues, Disney is undervalued.

''Disney remains a totally unique franchise with very significant asset values,'' he said. ''They are trying to be creative again instead of milking the old theme parks.''