. Based on 3D point-cloud data of human body, this paper probes rules research on width of pieces of pants. First, get the point-cloud figure of the studies through scanning the human body by 3D body scanning device (symcad). Read and optimize the point-cloud data by imageware software and obtain the total girth and the front/back girth of waist, abdomen, buttocks, thigh, knee and ankle. Then set the coefficients to establish the regression equation by using SPSS. Finally, verify the above-mentioned method through other studies to illustrate its feasibility. This study completes part of the work for the conversion from 3D garment pattern to 2D, to make up that the 2D non-contact body measurement system cannot directly obtain 3D sizes, and provides the basis for automatically pattern generation of pants.