Microorganisms are nutritious resources for various soil fauna.Although soil fauna grazing affects microorganism composition and decomposition rate,the responses of soil fauna and leaf litter decomposition to added microorganism is little understood.In this study,in the coniferous and broad-leaved mixed forest of Tahe County in the northern Da Hinggan Mountains,China,three sampling sites(each has an area of 10 m2) were selected.The first two sites were sprinkled with 250 times(EM1) and 1000 times(EM2) diluted effective microorganism(EM) preparations evenly,and the third site was sprinkled with the same volume of water as a control site.The responses of soil fauna structure and leaf litter decomposition to EM treatment were conducted during three years.The results revealed that EM treatment resulted in significant increase of soil organic matter.The number of soil fauna in the EM1 and EM2 sites increased by 12.88% and 2.23% compared to the control site,and among them springtails and mites showed the highest increase.However,the groups of soil fauna in the EM1 and EM2 sites decreased by 6 and 9,respectively.And the changes in the diversity and evenness index were relatively complicated.EM treatment slowed the decomposition of broad-leaved litter,but accelerated the decomposition of coniferous litter.However,the decomposition rate of broad-leaved litter was still higher than that of coniferous litter.The results of this study suggested that the added microorganisms could help individual growth of soil fauna,and this method led to a change in the process of leaf litter decomposition.This paper did not analyze the activity of soil microorganisms,thus it is difficult to clearly explain the complex relationships among litter type,soil fauna and soil microorganisms.Further research on this subject is needed. Microorganisms are nutritious resources for various soil fauna. Though soil fauna grazing events microorganism composition and decomposition rate, the responses of soil fauna and leaf litter decomposition to added microorganism is little understood. In this study, in the coniferous and broad-leaved mixed forest of Tahe County in the northern Da Hinggan Mountains, China, three sampling sites (each having an area of ​​10 m2) were selected. The first two sites were sprinkled with 250 times (EM1) and 1000 times (EM2) diluted effective microorganism (EM) preparations evenly, and the third site was sprinkled with the same volume of water as a control site. responses of soil fauna structure and leaf litter decomposition to EM treatment were conducted during three years. The results revealed that EM treatment resulted in a significant increase of soil organic matter. the number of soil fauna in the EM1 and EM2 sites increased by 12.88% and 2.23% compared to the control site, and among them springtails and mit es showed the highest increase. Host, the groups of soil fauna in the EM1 and EM2 sites decreased by 6 and 9, respectively. And the changes in the diversity and evenness index were relatively complicated. EM treatment slowed the decomposition of broad-leaved litter , but accelerated the decomposition of coniferous litter. However, the decomposition rate of broad-leaved litter was still higher than that of coniferous litter. The results of this study suggested that the added microorganisms could help individual growth of soil fauna, and this method led to a change in the process of leaf litter decomposition.This paper did not analyze the activity of soil microorganisms, thus it is difficult to clearly explain the complex relationships among litter type, soil fauna and soil microorganisms .Further research on this subject is needed.