Cover crop can be used to suppress weeds by competition for light and nutrient. Objective of this study was to evaluate the effectiveness of legume cover crops on change of weed community in no-till corn cultivation. Two legume cover crops, hairy vetch and crimson clover were grown in the field, and succeeding corn was sown on 4 May, 2010. The distribution of weed was surveyed at 15 April, 1 June, and 20 August. At 15 April, the weed biomass in hairy vetch field was higher than in crimson clover field. The dominant weeds were Capsella bursa-pastoris L. and Stellaria aquatica L. in hairy vetch and crimson clover fields, respectively. At vegetative stage of corn, occurred weeds in hairy vetch and crimson clover fields were four and six species, respectively, while the weed was occurred with nine species in conventional. Also the dry weight of weed was decreased by 82 and 75% in hairy vetch and crimson clover fields compared to conventional. On the other hand, after harvest of corn, occurred weed in hairy vetch, crimson clover and conventional was five, four and five species, respectively. Dry weight percentage of occurred weed in conventional was 23.5%, and the value was higher than 13.8 and 14.7% in hairy vetch and crimson clover fields, respectively. Stellaria aquatica L. as winter annual weed only occurred in cover crop field during corn growing season. It is these possibilities that low soil temperature and light interception by soil cover of legume cover crop.