Based on a 10-year long-term experiment，nitrogen uptake and utilization and changes of soil nitrogen pool in wheat-maize rotation system with 0，120，240，360 and 600 kg/hm² of organic nitrogen treatments were studied to analyze and evaluate the effects of long-term application of organic fertilizer on nitrogen absorption and utilization，soil residual rate and loss rate and to explore the use of nitrogen balance to estimate nitrogen efficiency as an evaluation index for application of organic fertilizer.The results showed:(1)With the extension of the time，the nitrogen surplus of treatments with 0，120， 240 kg/hm² organic nitrogen increased year by year，and then reached a relatively stable state；the nitrogen surplus of treatments with 360 and 600 kg/hm² organic nitrogen exceeded 50% of the corresponding nitrogen application amount each year. (2)The content of soil nitrogen increased year by year，and the greater the amount of nitrogen applied，the greater the increment is 10 years later，the soil nitrogen content of different organic fertilizer treatments tended to be stable.(3)10 years later，the nitrogen use efficiency of treatment with 120 kg/hm² organic nitrogen was about 75%；the nitrogen use efficiency of treatment with 240，360 and 600 kg/hm² organic nitrogen was maintained at about 60%，45% and 30%，respectively；the residual rate of nitrogen was between 10% and 15%；the nitrogen loss rate of treatment with 120 kg/hm² organic nitrogen was about 10%，and that of treatment with 240 kg/hm² organic nitrogen was 30%.The nitrogen loss rates of the treatments with 360 and 600 kg/hm² organic nitrogen were about 45% and 60%，respectively.The soil system was basically stable after 10 years of long-term organic fertilization in winter wheat-summer maize rotation system.When 240 kg/hm² organic nitrogen was applied each rotation，the annual nitrogen surplus was about 250 kg/hm²，the residual nitrogen in soil was about 80 kg/hm²，and the nitrogen losses was about 180 kg/hm².The corresponding nitrogen use efficiency，residual rate and loss rate were about 60%，10% and 30%，respectively.Using nitrogen balance to estimate nitrogen efficiency can be used as an index to evaluate the application of organic fertilizer.