It is of great significance to investigate the impacts of biochar on the quantity of major nitrogen forms and conservation mechanism of nitrogen during aerobic composting of chicken manure, which could provide some theoretical supports for future study on NH3 emission, nitrogen loss, and composting process optimization. Chicken manure and wheat straw were used as primary materials, and proper amount of biochar was added to conduct aerobic composting with an intelligent aerobic composting reactor system. Based on the physicochemical and biological indicators and dynamic data of major nitrogen forms, combined with analysis of scanning electron microscopy and the quantity variation of main microbial communities, the quantity variation of major nitrogen forms was studied and the conservation mechanism of nitrogen was illustrated. Conclusions were drawn as follows: adding proper amount of biochar could yield less NH3 emission and nitrogen loss;there were significant positive correlation between NH+4-N concentration and NH3 emission (r=0.783, p=0.037<0.05). There were highly significant negative correlation between NO-3-N concentrationand NH3 emission (r=-0.941, p=0.017<0.05). The results showed that cellular structure of biochar could effectively adsorb various nitrogen such as NH3 and NH+4-N, reduce NH+4-N concentration in the pile, and thus reduce the NH3 emission effectively. In addition, biochar could provide appropriate refuge for nitrifying bacteria, promote the nitration reaction, and then inhibit NH3 volatilization.