In the teaching of design courses, the process of students to complete the designs is considered more important than the final results, and usually there are no standard answers for these designs. Thus, the research on the process evaluation method in design courses is of great significance. Taking the assessments of two design courses in optical discipline as examples, the psychophysical experimental methods are introduced into the process evaluation of the design courses, i.e. the process evaluation given by each student to others in forms of classification, sorting or grading are adopted as one trial of a psychophysical experiment, which generate many experimental data of mutual evaluation. Based on these data, evaluation results are measured scientifically using the statistical method. Furthermore, through correlation analysis and regression analysis of these data, the relationship among various aspects of different process can be studied. It is easier for students to understand and accept their assessment results, and more helpful for teachers to analyze the influencing factors in their teaching process.