The aim of this study was to compare the electromyography of leg muscles and the peak vertical ground reaction forces during single leg drop landing of men with genu varum deformity and normal knee. 26 physical education male students participated in this research, including 13 subjects with genu varum and 13 with normal knee. Electromyographic activity of some leg muscles along with the data of ground reaction forces were measured. Genu varum deformity was measured and recorded by a caliper. Subjects performed single-leg landing from 30cm height onto a force platform. Landing motions were divided into two phases: 100 ms preceding ground contact and 100 ms after ground contact (absorption phase). Independent t test was administered for the statistical analysis of data using SPSS software 16 (P?0.05). The results showed no significant difference in the activity of the soleus, medial gastrocnemius and anterior tibialis muscles during pre-landing phase ((P?0.76), (P?0.09) and (P?0.77) respectively). No significant difference was found in the activity of soleus and anterior tibialis muscles during absorption phase ((P?0.68) and (P?0.92) respectively). However, the activity of medial gastrocnemius was significantly different between the groups (P?0.04). No significant difference was found in the peak vertical ground reaction force during metatarsal contact (P?0.22). However, the peak vertical ground reaction forces in calcaneus contact (P? 0.003) between the groups were significantly different. The results showed that subjects with genu varum had lower activity in medial gastrocnemius muscle during the absorption phase of landing which may insert bigger forces into their lower extremity in comparison with normal subjects; in long-term, this may result in injury and occurrence of articular degenerative diseases.