Abstract: In order to further explain the mechanism of allelopathy and provide some theoretical reference for plant configuration and maintenance management of urban green space in the future. Soil samples were treated with gradient concentration of water extracts from Ophiopogon japonicus, and the community structure characteristics of small and medium-size soil fauna were analyzed. The results showed that: (1) A total of 3148 small and medium-size soil fauna were captured, belonging to 14 orders and 39 families. (2) There were significant differences in the number of individuals of small and medium-size soil fauna under different concentrations of water extracts (P<0.05), which usually decreased with the increase of concentration of water extracts. (3) There were significant differences in the community structure of small and medium-size soil fauna under different concentrations of water extracts (P<0.05). (4) The community diversity of small and medium-size soil fauna decreased with the increase of treatment time. (5) The small and medium-size wet soil fauna were more sensitive to the water extracts of allelochemicals than dry soil fauna. Our study indicated that the allelopathy of O. japonicus can affect the diversity characteristics of small and medium-size soil fauna communities. The long-term effects of plant configuration and soil fauna should be considered comprehensively in practical application, and the planting density should be paid attention to build a sustainable green landscape.