The purpose of this paper is to establish a criterion for the school chair surface evaluation through analyzing the rules between contour features and the comfort base on experiments. In the paper, 5 basic contour feature parameters, which are buttocks plunging depth, thigh plunging depth, buttocks contour width, buttocks contour deep and thighs contour width, are proposed. Maximum peak stress (Pm) and contact area (S) are adopted as comfort indices. The participants are 50 Chinese high school students (29 boys, 21 girls) who grouped by body size. Through carrying out the experiments of body pressure distribution at different seat contours, all participants require expressing their feeling about sitting, the effect rules of the basic contour feature parameters on seated comfort are obtained. The results shows the different value of buttocks contour deep and thighs contour width leads to varying optimal comfort points corresponding to different somatotype people. According to BP neural network, a prediction model is established. Finally a kind of school chair surface evaluation criterion based on contour is put forward.