In the context of the current rapid increase of anthropogenic nitrogen input in global ecosystems, clarifying the relationship between biological nitrogen fixation and available nitrogen has important guiding significance for the estimation of ecosystem nitrogen budget and the optimization of fertilization strategies. This article reviews the research on the effect of available nitrogen on biological nitrogen fixation at the molecular, individual and community scales, and compares the studies on the three scales. We found that the current molecular and individual-scale related research is more systematic, but is severely limited to the cultivation of nitrogen-fixing bacteria; although the community-scale research is carried out by non-cultivation technology, the research efficiency is relatively higher, but the research on the expression of nitrogen-fixing genes is not It is very scarce, and the research system needs to be improved urgently. Accordingly, future research should pay more attention to the regulation of nitrogen fixation gene expression at the community scale by available nitrogen, and focus on improving the research system of community-scale biological nitrogen fixation.