Abstract: According to analyzing the body surface and section shape of the male lower limbs,the different split structure and the shape characteristic of the male underpants were thoroughly studied.Connected planar structure, half the three-dimensional structure of the two pieces form combination, three-dimensional structure of the three pieces form combination and the separate structure were put forth to reveal the four different kinds of split structure characteristics, the application method and the rule of the split structure in the male orthopedic underpants were discussed.The research indicated that, the male underpants' construction shape is determined by the split structure, the split degree is higher and the three-dimensional effect is better, the split degree is lower and the shape is more towards complanation, the crotch point is moved forward and the male physical characteristics is more obvious , the crotch point is moved backward and the male physical characteristics is fuzzier. The application of the split structure in the male orthopedic underpants can be divided into the partial split structure of highlighting shape and the partial planar structure of concealing shape.

Key words: men's underpants, thighs, split structure, crotch point, three-dimensional reduction