Abstract: Rice-crab co-culture (RC) is a new eco-agricultural process in paddy cultivation and breeding models. It has been significantly promoted in the development of eco-agricultural programs. Recent studies, which concern the RC system, mainly focus on the effects of multiple factors on crab or rice production. However, studies on the community of natural enemies in RC ecosystems are still rare. The goal of this study was to determine the regulation of occurrence, composition, and diversity of spider communities in crab paddies and conventional paddies. Suction samplers were applied to collect spiders in the paddies. Species composition and diversity of spiders were recorded and analyzed. The results showed that:1) 31 species and 11 families of spiders were found in both paddies. Three major families of spiders, Lycosidae, Linyphiidae, and Araneidae, accounted for at least 70% of the spider populations. 2) The number of individual spiders in the crab paddies was significantly higher than that in conventional paddies. 3) The Shannon-Wiener index indicated that the diversity of spider species was highest from August through September, and lowest in early June. Furthermore, the results showed that the Shannon-Wiener indexes were positively correlated with Pielou's or Margalef's indexes but were negatively correlated with the Simpon's indexes. The results revealed that there was no difference in the numbers or diversities of spider species between crab paddies and conventional paddies, whereas the difference in the number of individual spiders was significant between the two paddy types. This study lays a foundation for the study of the biodiversity characteristics of arthropods in RC systems.