In order to explore the decomposition process of straw in the double cropping rice region，the nylon mesh bag method was used to study the effects of different types of rice straws returned at different buried depths (0，10 cm) on the straw decomposition and nitrogen and carbon release.The results showed that after 90 days of decomposing for early season rice and 120 days for late rice，the average decomposing rates of early season rice and late rice were 64% and 72%，respectively.Straw decomposed faster in the first 15 days of returning to the field，and slowed down in the later 30～90 (120) days.The decomposing rate of straw in late rice season was higher than that in early rice season，besides，conventional Indica Rice was higher than Indica Hybrid Rice.And Hybrid Indica Rice was higher than Hybrid Japonica Rice.Meanwhile，the decomposing rate of surface straw was slightly faster than that of deeper straw.At the end of the rice growth period，the nitrogen release rate of the straw was 60%～70%，and the carbon release rate of the straw reached 70%～80%.Different depths had no significant effect on the carbon and nitrogen release rate of straw，and the carbon release in the soil surface layer was slightly faster.