Abstract:The introduction of chemical nitrogen fertilizer has greatly increased the crop yield. However, the excessive fertilization or improper fertilizer use will cause severe damage to the agro-ecology system. Understanding characteristics of plants and seeking alternative nitrogen (N) sources are crucial to reduce the use of fertilizer and increase nutrient efficiency. The biological nitrogen fixation established between plants and microorganisms can provide a large amount of clean N sources for the host, which plays an irreplaceable role in agricultural production. Here, we take sugarcane as an example to summarize the progresses of the associative N2 fixation, including the discovery, screening, infection mechanisms and functional study of plant-associated N2-fixing bacteria, and the application of the mixed inoculations with diazotrophic bacteria in sugarcane production. We predict that these will provide theoretical basis and reference value for improvement of nutrient efficiency and promotion of biological nitrogen fixation in agricultural production.