In order to have a clear idea about the carbon cycle in the agro-ecological system of China,the uptake, emission,fixation and transfer of CO2 by the system in the years 1990 and 2000 are calculated and analysed,and a schematic map of carbon cycle in the agro-ecological system of China is drawn. The results indicate that the percentages occupied by the emission amount,fixation amount and transfer amount are 89. 7% 91.0% and 9.12% of the uptake amount respectively in the year 1990,and they are 7.83%, 1.18% and 1.16% respectively in the year 2000. It can be seen clearly that the CO2 uptake amount of the agro-ecological system of China is greater than the CO2 emission amount,and the system is a"sink"but not a"source"in respect to the atmospheric CO2 concentration in both the current periat and the peried after climatic change.