Abstract: Nitrogen plays an important role in plant growth and development, and there is less available nitrogen in soil that can be directly used by plants. At present, chemical fertilizer is mainly used to increase the content of available nitrogen in soil, but the excessive application of common chemical fertilizer has certain negative effects on soil, air and water environment. The research and application of functional microbial fertilizer can reduce the harm of chemical fertilizer and improve the content of available nitrogen in soil. In this study, nitrogen fixing bacteria in soil were screened by ashube culture medium, and their tolerance to extreme environment was investigated. Corn straw powder, fermented cow dung and rice husk were selected as the carrier of bacterial fertilizer to explore the best conditions for the preparation of bacterial fertilizer. The microbial fertilizer was applied to coastal saline-alkali soil and its effect on the basic properties of the soil was measured and analyzed.