The diversity and community structure of arthropods in an organic double-cropped rice ecosystem in Guangdong Province, China was studied. We compared the arthropod communities in the early season (Apr–Jul) crop to those in the late season (Aug–Nov) crop in 2009. The comparisons were undertaken using a combination of community assessment approaches, including morphospecies richness, the Shannon-Weaver diversity index, H', the Pielou-evenness index, J, the Simpson dominance index C, the Jaccard similarity index q and the compositions of the sub communities. We collected 114 species of arthropods, which consisted of including 58 species of spiders, 16 species of predatory insects, 25 species of phytophagous insects, 15 species of neutral/other insects, in early season crop. Subsequently we collected 109 species of arthropods, which consisted of 50 species of spiders, 19 species of predatory insects, 24 species of phytophagous insects, and 16 species of neutral/other insects, in the late season crop. There were no significant differences (P < 0.05) between the arthropod communities of the early and late season rice crops with respect to the Shannon-Weaver diversity index, the Pielou evenness index and the Simpson dominance index. Moreover the Jaccard similarity index in early and late season rice was as high, i.e., 0.70. The spider sub community had the greatest number of species in both rice crops, but the phytophagous insect sub community had the largest number of individuals in both rice crops. The dominance of predatory insects in the early season rice crop was significantly lower (P < 0.05) than in late season crop, but there was no significant difference in the composition of the neutral/other subcommunity between the early and late season rice crops.