Determination of soil organic C content at steady state is of important significance for evaluating potential of C sequestration of the soil and developing a measure for rational organic material utilization.In this study,change in soil organic C content of paddy fields in a typical red soil region over a period of time,dynamics of the organic C content in the paddy soils across a chronosequence of cultivation,and the input and output of soil organic C,were investigated in order to determine the organic C content at steady state and then potential of C sequestration in the paddy soils of subtropical China.In the past 20 years or so,soil organic C content of the paddy fields in Yujiang County of Jiangxi Province increased generally but it remained stably at 18.5 g kg^-1 in paddy soils with high productivity.After 30 years of rice cultivation,soil C content of the paddy field reached to 19.0(±1.20)g kg^-1 and varied insignificantly afterwards.If the high level of soil organic C formed recently is settled in equilibrium,the soil organic C content will be 19.2(±1.10)g kg^-1.As a whole,at the present high level of productivity,the soil organic C content at steady state of paddy soils in subtropical China would be 18～20 g kg^-1 with an average of 19.0 (±1.0)g kg^-1.In the past 20 years,the storage of organic C in the paddy soils of Yujiang County increased by 6 955 (±1 116)kg hm^-2.Based on this,it was figured out that the paddy soils in subtropical China sequestrated 555.1(±88.7)Tg of atmospheric CO₂ in the past 20 years,demonstrating an important function as a sink of CO₂.Today there are still large areas of paddy fields that have less soil organic C content than that at steady state.It is estimated that they could sequestrate on average 5 150(±1 063)kg hm^-2 more of carbon.Therefore,at the present high level of productivity,the paddy soils in subtropical China would sequestrate an extra of 411.0(±84.7)Tg of atmospheric CO₂ in future.