Abstract:To understand the input and utilization of nitrogen in crop production-livestock breeding system in the area of Xiaoxing'an Mountains of northeast China, Dailing District of Yichun City was selected as the study area. The material flow analysis method was used to decipher the processes of nitrogen input, migration, transformation and output, nitrogen flux, production efficiency and environmental load in crop production-livestock breeding system were calculated. The results showed that from 2007 to 2015, nitrogen flux per unit area of the crop production system and the livestock breeding system tended to increase, which was more obvious from 2007 to 2012. The quantity of livestock breeding and cultivation structure of crops were important factors affecting nitrogen flux. The average nitrogen utilization rate of crop production system was 64%, indicating that crops could effectively use nitrogen. The nitrogen utilization rate of livestock breeding system was only about 19%, which remained large space to promote. The environmental nitrogen load increased year by year, which was attributed to nitrogen loss of manure and urine resulted from the rapid increasing number of livestock breeding. To reduce the environmental nitrogen load for the efficient and sustainable development of the crop production and livestock breeding systems, it is necessary to strengthen the management of livestock breeding, reasonably control the number of livestock and poultry, improve the utilization of manure and urine, meanwhile reduce the input of fertilizer-sourced nitrogen.