Abstract: Biochar is a kind of highly aromatized insoluble solid matter produced by pyrolysis of biomass materials under partially or completely anaerobic conditions. Biochar application can change soil physical and chemical properties, strongly affect the habitat of soil microorganisms, influence the community structure and activity of microbes for soil nitrogen fixation, nitrification and denitrification, and thus affect the main processes of soil nitrogen cycle (nitrogen fixation, nitrification, denitrification, etc.). This paper reviews the published literaturerelated to the effects of biochar application on the main processes of soil nitrogen cycle and their microbial functional genes. The analysis results indicate that biochar application improves soil permeability, raises soil pH value and the effectiveness of soil carbon and nutrients, and significantly increases soil N fixation by 15%-227%, soil nitrification rate by 28%-200% respectively. But it reduces 20%-73% of the total soil ammonia volatilization accumulation and 11%-78% of the soil N₂O emission accumulation. In addition, biochar application increased the gene abundance of nifH and amoA and then promotes nitrogen fixation and nitrification in the soil, The biochar application also increases the gene abundance such as nosZ and the activity of N₂O reductase fittable for the denitrification of soil (final conversion of N₂O to N₂) and suppressed N₂O emissions. And this effect will become stronger with the increase of biochar application rate. Furthermore, impact of biochar application on the soil nitrogen cycling and its functional microorganisms depend on the types of biochar raw materials and production conditions. Different kind of regulatory genes have different contributions to the soil nitrogen cycling. Under the action of biochar, the soil pH value and nutrient availability increases, and AOB may contribute more to soil nitrification than AOA. Compared with other regulatory genes (narG, nirS, nirK), the gene nosZ seems to be more important for the soil denitrification. Therefore, t is necessary to further explore the effects of the biochar application on microbial functional genes for soil nitrogen cycling, especially the specific contribution of different kinds of functional genes to the nitrogen cycling process and factors influencing them in order to deepen the identification of them.