Abstract: In this paper,three kinds of forest gaps with different area (L₁:50 m², L₂:100 m², L₃:150 m²) were set in a 50-years old Picea asperata plantation,and at the same time,the forest without cutting was set as control (CK). The soil was sampled in different soil layers(0~5 cm,5 cm~10 cm,10 cm~15 cm),and then was determined by adopting chloroform fumigation, aiming to study the effect of forest gap improvement on carbon and nitrogen content and vertical distribution of soil microbial biomass. The results showed that the forest gaps had significantly increased the contents of soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN), and the bigger the gap's area was, the more the increase effect was. The contents of SMBC and SMBN in each soil layer was L₃ > L₂ > L₁ > CK. In the three kind of gaps and CK,the contents of SMBC and SMBN decrease with the increase of soil depth, but in the 0~5 cm layer, the bigger the gap's area was, the proportion of the content SMBC and SMBN would become less.