Abstract: Nitrogen loss during composting not only reduces the quality of the compost, but also pollutes environment. To study nitrogen transformation and proper measures of nitrogen conservation during composting, the authors summarized ammonification, ammonia assimilation, nitrification, denitrification and struvite formation in compost. Factors such as C/N ratio, pH value, temperature and ventilation influencing nitrogen loss during composting were also analyzed. Measures like regulating C/N ratio, inoculating microbial agents, adding adsorbents and chemicals, and controlling ventilation for controlling nitrogen loss were demonstrated. In future, further studies should be carried out on the C/N ratio based on the form of carbon and nitrogen, the microbiological mechanism of nitrogen transformation and the technology for minimizing nitrogen loss that suitable for large-scale composting production.