Abstract: In this paper, starting from farmland planting, quantity variation roles of three major microorganisms of Datong farmland in different fertility, different crops, different intercropping condition and its effect on wheat yield was studied. The results showed that fertilization can significantly promote root growth, and thus increase the number of microorganisms;Intercropping of wheat, alfalfa, soybean and rape could increase the number of soil microorganisms in wheat rhizosphere;The number of three microbial populations was the highest in bacteria in Datong field, followed by was actinomycetes, fungi number was the least.