Purpose : The purpose of this study was to investigate the effect of cross bag weight and carrying bag position type on vastus medialis oblique and vastus lateralis muscle activity ratio during step up. Method : Twenty healthy subjects participated in this study. subjects randomized performed step up with bag weight less than 15%, more than 15% of totalbody weight and without bag and carrying bag position ipsilateral and contralateral. muscle activity was measured with surface electromyography. One-way analysis of variance with repeated measures was used with a significance level of 0.05 Result : The results of this study were as follows: 1. The muscle activity ratio decreased significantly ipsilateral bag position more than 15% of body weight(p<.05). Also, the muscle activity ratio increased significantly contra lateral bag position more than 15% of body weight(p<.05). Conclusion : In conclusion, it was found that applied carrying bag position with weight on VMO,VL muscle activity ratio during step up down. Therefore carrying bag position can be used to selective activate vastus medialis oblique muscle in subjects with patellofemoral pain syndrome.