Abstract: To screen for a selective medium suitable for cultivation of bacteria, fungi and actinomycetes in the soil, 19 types of medium were tested. Beef extract peptone medium+Jia Shuang Shuang Mei, Mading medium+1 mL 1‰ rose bengal and Martin medium+0.1 g potassium dichromate were best for culturing bacteria, fungi and actinomycetes. The numbers of bacteria, fungi and actinomycetes were counted after Trichoderma aureoviride T2 strain was applied to the lawn soil. T. aureoviride cause significant changes in the microbial community structure. Seventeen days after T. aureoviride was applied, the number of fungi decreased by 4 001 cfu/g but the number of bacteria increased by 1.27×10¹⁰ cfu/g compared with the control, while the number of actinomyces did not change significantly. The ability of T. aureoviride colonisation demonstrated that T. aureoviride could colonise the soil of turf grass within one month. Twenty five days after T. aureoviride was applied, the relative content of T. aureoviride was the lowest, but 5 days later it increased and then remained stable.