Abstract: It is essential to develop the fit female upper garment prototype which suits the body features of the female,for it requires high degree of fitness and flexibility.Through the calculation of stepwise regression by C ++,tries to establish the computation relationship between the control part of fit female jacket and the crosswise part.Through comparison of the stepwise regression math models of different body forms and crosswise parts,it indicates that the waist size has great influence on the crosswise specifications.The conclusion provides pattern making experience for the garment enterprise and a theoretical basis for applying CAD technology to the designing of clothing prototype.