The singularity of biological characteristic, selectivity of nutrient absorption and utilization and particularity of environmental effect under the artificial pure forests usually result in the polarization of soil properties, which is one of the basic reasons leading to soil degradation. The measurements of soil properties of several typical artificial pure forests（larix kaempferi，Pinus tabulaeformis，Catalpa fargesii，Quercus. aliena var. acuteserrata) in north mountains of Qinling showed that: 1) in the development from the natural grassland to the artificial conifer forests, soil properties generally worsened, such as acidification, decreases of soil nutrients and microorganism biomass, but partial enzyme activities improved. Meanwhile, in the development from the natural grassland to the artificial broadleaf forests, soil properties generally improved, such as neutrolization of acidity, enrichment or polarization of soil nutrients. 2) in the development from the natural grassland to the artificial pure forests, the order of absolute comprehensive polarizations of soil properties was: enzyme activity＞microorganism biomass＞nutrient contents＞physical properties＞pH, thereinto, the order of absolute comprehensive polarizations of soil physical properties was: conifer forest＞broadleaf forest, and the order of absolute comprehensive polarizations of soil microorganism biomass was: conifer forest＜broadleaf forest, but the polarizations of soil nutrient contents and enzyme activity varied with the types of artificial forests, and C．fargesii forest showing the greatest polarization, while Q. aliena forest the lest.