Wetland is a sort of special soil resources and ecosystem, the basic function of which is to adjust the water circle and maintain the habitats for special animals and plants. Wetland is also a special and effective ecosystem between water and land, in which insects play a very important role. But is not deeply and not be utilized amply. North Dagang wetland nature reserve is situated in the southeast of Tianjin (38°36′～38°57′N, 117°11′～117°37′E). It is the biggest wetland nature reserve in Tianjin. The relative altitude is 2～6 m. And has more important wetlands, which are indispensable areas of the flyway for the Asia-Pacific migratory birds as well as a temporary habitat for the migrating birds in severe danger, such as Grus vipio and G. japonensis. In order to identify the moth species and study their dynamic laws, select the indicator insects to indicate the wetland quality, provide service for studying and protecting the wetlands. An investigation on the diversity of moths’ community was carried out from June 12 to October 14 in 2001 and from April 12 to October 30 in 2002. A total of 132 moth species belonging to 105 genera in 17 families were collected. Noctuidae is the major family in quantity. Crambidae, Pyralidae, Geometridae and Tortricidae are also abundant year around. Data of insects collected during the survey were listed and constructed on the speciesabundance, the indices of diversity (H′), evenness (J′), specific richness (S) and individual number (N) according to the Excel. And the status of the wetland has been analyzed by using the curve of the moth community speciesabundance, the indices of diversity, the connection of the evenness and the indices of diversity etc. The results show that the curve of the moth speciesabundance was in accordance with the nichepreemtion hypothesis. And no significant correlation was found between indices of diversity and evenness (r=0.21) but indices of diversity and richness was significantly correlated (r=0.90). The reason for this is that the speciesabundance curve was in accordance with the nichepreemtion hypothesis which shows the moth species in North Dagang wetland reserve was not rich, and the moth community of the wetland was unstable. In other words, the entironment that the moth depend on was unstable. This suggests that the environmental quality of the North Dagang wetland is unstable. It due to the serious degeneration of the wetland environment and the interference of human activities.