Purpose The purpose of this study was to identify the effects of treadmill according to walking direction on the affected side lower limb muscle activity and walking characteristic in stroke patients. 30 patients who consents were randomized as two group. Methods The Forward Walking group and Backward Walking group performed gait training using on treadmill and conventional physical therapy. Results To find out the effect, affected side lower limb muscle activity by BTS Free EMG 1000, walking characteristic by Gait Trainer 2 were three times repeatedly measured at baseline before and after. The results of this study were summarized as follows: Forward walking group improved more significantly 6 weeks after treatment quadriceps, hamstring, tibialis anterior and gastrocnemius in affected side sEMG. Backward walking group improved more significantly 6 weeks treatment quadriceps, hamstring, tibialis anterior and gastrocnemius in affected side sEMG. After a 6 weeks treatment, there was no difference between the two groups in the sEMG. But quadriceps, tibialis anterior and gastrocnemius in the forward walking group showed a mean difference between the positive effects higher than backward walking. Forward walking group improved more significantly 6 weeks after treatment walking speed and walking cycle in gait charateristic. Backward walking group improved more significantly 6 weeks after treatment walking speed, walking cycle and affected side stance phase symmetry index in gait charateristic. After a 6 weeks treatment, there was no difference between the two group gait characteristic but walking speed, walking cycle and step length symmetry index in the backward walking group showed a mean difference between the positive effects higher than the forward walking group. Conclusion To summarize the result of this study, it is considered that forward walking and backward walking contribute to improve affected side lower limb muscle activity, walking speed and walking cycle. And backward walking contribute to improve affected side stance phase symmetry index.