In this study, the fuzzy inference technique was applied for preprocessing the clinical drawings of schizophrenic patients. The interpretation procedure for the clinical drawings was divided into two phases, namely preprocessing and interpretation phases. In the preprocessing phase, two analyses were conducted by employing the fuzzy inference technique and three analyses were conducted by applying Fourier transform, wavelet transform, and singular value decomposition on three images of the tree test. In the interpretation phase, the drawings and output images were psychologically interpreted. The contrast of each image was also examined for determining the feature associated with the corresponding output image of the fuzzy inference technique. Based on the compared interpretations and contrasts, it can be concluded that image analysis incorporating the fuzzy inference technique is superior as a preprocessing method employed before interpreting whole image. Further research is required for examining the relation between the empirical findings regarding schizophrenic patients and the parameter of the fuzzy inference technique.