The purpose of this study was to develop slacks patterns for obese-schoolgirls aged 10~12 by using a 3D virtual garment simulation system. The criteria for subjects in this study were girls who had a BMI of over 25kg/m2. A total of 155 schoolgirls who met these criteria were enrolled. The results were as follows: First, by using 3D virtual garment simulation, a new slacks pattern considerate of obese-schoolgirls was developed. The basic numerical formulae were as follows: Front and back hip girth of H/4－0.5+1 and H/4+0.5+1.5, front waist girth of W/4+1+0.5, back waist girth of W/4+2+0.5, front crotch extension of H/16－0.5, back crotch extension of H/8－0.5, front dart amount of 1, and back dart amount of 2. Second, according to the new slacks pattern appearance evaluation, the new slacks pattern scored more highly than the existing pattern for silhouette and ease amount, confirming that the new slacks pattern is appropriate for obese-schoolgirls. Additionally, the new slacks pattern was evaluated allowing for the proper space length of the waist, abdomen and hips. This study is expected to serve as important basic data for ensuing studies that may utilize a 3D virtual garment simulation system with 2D patterns and for future 3D pattern production program development.