PURPOSE: The object of the present study is to investigate the effects of the insole supporting medial longitudinal arch while walking in spastic cerebral palsy with pes planus. METHODS: Ten spastic bilateral cerebral palsy children with pes planus participated in this study. The insole were custom-made for the individual child. Muscle activity was measured by surface EMGs attached on tibialis anterior (TA), gastrocnemius (GA), vastus medialis oblique (VMO), biceps femoris long head (BF). temporal-spatial parameters such as velocity, step length, stride length, stance time, toe angle were collected while the subjects walked on the GAITRite system. RESULTS: The results of the present study were summarized as follows: 1. Muscle activities in mean EMGs while walking: Left VMO, Right TA, Left BF and GA revealed significant reductions after applying insole. 2. Muscle activities in peak EMGs while walking: Left TA and BF demonstrated reductions significantly after applying insole. 3. There were improvements in temporal-spatial gait parameters with insole: velocity, both step length, Right stride length and Right toe angle were increased(p<.05). CONCLUSION: Therefore the current study demonstrated that insole supporting the medial longitudinal arch would be effective on gait of the spastic cerebral palsy with pes planus.