Abstract: To understand the effect of soil fauna on nitrogen(N)mineralization under different land uses, we conducted experiments at three different land use patterns(i.e. poplar plantation, cropland and crop-poplar integrated system)with three treatments including control, nematodes exclusion and soil fauna exclusion in the coastal area of northern Jiangsu Province. The variations of soil net N mineralization rate were analyzed with a closed-up incubation method. The results showed that in three different land use patterns, the soil NO^-₃-N and total mineral nitrogen(TMN)contents in nematode and fauna exclusion treatments were all significantly lower than that in control, which indicated that the soil fauna and nematodes might significantly increase the contents of NO^-₃-N and TMN, while the content of NH⁺₄-N had no significant difference.The pattern of land use, soil fauna groups and their quantities also affected the soil net N mineralization rate. In 0-10 cm soil layer of all the land use patterns, the net N mineralization rate of the control treatment decreased in the order of cropland, poplar plantation and crop-poplar integrated system. With nematode exclusion and fauna exclusion, the order changed to crop-poplar integrated system, cropland and poplar plantation. However, there was no significant difference for 10-25 cm soil layer of all land use patterns. When the poplar plantation and cropland were 0-10 cm in depth, nematode exclusion treatments led to a significant difference of net N mineralization rate when compared with the control group. Both nematode and soil fauna exclusion were found to be able to lower the net N mineralization rates. Moreover, the microbial biomass nitrogen contents in soil with fauna exclusion treatments were extreamly significantly lower than that in the control, which indicated that soil fauna exclusion might extreamly significantly influence soil microorganisms.