The use of milk vetch as winter green manure is common in paddy fields across southern China. The greenhouse effect of co-utilizing milk vetch and rice straw has not yet been reported. In this study, we investigated net greenhouse gas emissions and related environmental factors over two years based on a long-term experiment. The results showed that the application of milk vetch increased rice yields and soil productivity, especially in combination with rice straw utilization. The application of milk vetch increased annual soil carbon sequestration rate by 492 kg/ha without rice straw returning and by 1115 kg/ha with rice straw returning. Compared to rice straw returning, cumulative CO