The soil nutrient

microorganism and enzyme activity are studied and analyzed in Pinus sylvestris var.mongolica plantations in Zhanggutai area. The results are as follows:the differences of microorganism quantity among different type of soil is the significant

so are the enzyme activity and soil nutrient. The correlation among soil microorganism quantity

enzyme activity and soil nutrient content is the significant

it can be used as evaluation index of soil fertility. The strategy and measures to prevent the soil degradation of Pinus sylvestris var.mongolica were put forward

including application of thinning rationally for existing dense plantations and establishment of mixture forest for new plantations.