A study using compare and analyze about differences among three basic pants patterns(shape and size of pattern, fitting and amount of air gap and so on) through 3D simulation. This study use 3D simulation program, DC Suite version 3.0. The results are as a follows: The results of comparison about total pants pattern shape, the ESMOD have two tucks of front and one dart of back and the Secoli and On&on have each dart of front and back. The results of estimation about total appearance, the On&on is the best of all pattern about total silhouette of front and back side and the ESMOD is the worst of all. In a case of the ESMOD, the thigh part has so many spaces between body and pants so it is rated low. When we examine about space between body and pants, amount of air gap of ESMOD is 0.6 at waist circumference and next is On&on(0.07). In case of hip circumference, the Secoli is 0.08 and the ESMOD is 0.14. The ESMOD`s amount of air gap is 0.32 at thigh circumference and 0.62 at knee circumference. The Secoli`s amount air gap is 0.26 at thigh circumference and 0.59 at knee circumference.