Abstract:The effects of soil microbes and soil enzyme activities on soil nutrient states and the growth of stands were studied in poplar stands mixed with different tree species during 1992- 1995. The experiment was disigned in five treatments and three replications. The stands were located in Daxing County, Beijing and Minquan County, Henan Province With an area of 1.8hm2 and 3.2hm2 respectively. The results are as follows: (1) The microbes quantity found increased in the mixed stands. There were obviously differences in the quantity of microbes among the five treaments (P= 79%). (2) The soil enzyme activities varied with treatments (P = 87%), the invertase and the ] were increased obviously in the treatments A and C. (3) The productivities of poplar mixed stands are closely correlated with the soil nutrient status, soil microbes and the enzyme activities.