The objective of this study is to evaluate effects of urban pavements on soil microbial biomass in different trees. In-situ simulation test was arranged in the suburb of Changping District, Beijing, China. Pine (Pinus tabulaeformis) and ash (Fraxinus chinensis) were planted at the 1.0 m×1.0 m density in three different treatment plots:pervious brick pavement (PP) with a permeability coefficient of more than 0.4 mm/s, impervious brick pavement (IPP) with a permeability coefficient near zero, and non-pavement for control (Ctr). Topsoil (0-20 cm depth) which includes rhizosphere (tree pool) and non-rhizosphere (0.7 m away from trunk) were analyzed by the chloroform fumigation and extraction methods for soil microbial biomass carbon and nitrogen. The results showed the following:compared to Ctr, the soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), MBC/OC (organic carbon) and MBN/TN (total nitrogen) in non-rhizosphere of pine and ash and MBN/TN in rhizosphere of pine were significantly decreased by PP and IPP treatments. The MBN, MBC/OC, and MBN/TN in rhizosphere of ash and MBC in rhizosphere of pine were reduced by PP treatment. The soil MBC and MBN which were changed by pavements were positively correlated to soil total carbon (TC), TN and OC, and the soil MBN was negatively correlated to soil moisture. In general, pavements adversely affect the soil microorganisms, especially in non-rhizosphere,which may further affect the nutrient cycle, tree habitat, and ecosystem service of urban green space at a large scale.