Abstract: Application of nitrogen fertilization is a key factor which affects the agricultural carbon balance, quantitative assessment of soil respiration and carbon balance under different nitrogen fertilizer levels are important to the protection of the ecological environment on soil fertility and regulation of carbon emissions. In this study, field tube experiment and field experiment were conducted to explore the dynamic changes of soil respiration rate and the carbon balance of agricultural ecosystem under different nitrogen levels. The results showed that, maize biomass (shoot and root) fixed the amount of organic carbon of 5660.71～8106.00 kg C/hm2. The total amount of soil respiration(carbon release) was 9209.04 ~ 16510.40 kg C/hm2. On bare land, the total amount of microbial respiration(carbon release) was from 2827.36 kg C/hm2 to 6951.68 kg C/hm2. Root respiration contributed 57.9% ~ 69.3% to the total amount of soil respiration. Under maize-plant condition, carbon balance of different growth stages changed significantly during different growth stages. In the jointing stage, net ecosystem productivity (NEP) were negative under all treatments，which indicated soil was the source of atmospheric CO2. In the tasseling stage and the mature stage, NEP were positive and the soil presented as the sink of atmospheric CO2. The trend of NEP were different with the increase of nitrogen fertilizer application in the three growth stages: nitrogen fertilizer application significantly decreased NEP in the jointing stage, however, in the tasseling stage and the mature stage, NEP in the treatment of the nitrogen fertilizer application was higher than that without N application.