Habitat fragmentation has important effects on the spider community; however, the few research studies in this area are mostly comparative studies between different forest types. In this study, we sampled spiders using Winkler traps six times from 2010 to 2011 (in three seasons, spring, summer, and autumn) on 16 land-bridge islands in the Thousand Island Lake, East China. We analyzed the species abundance, diversity, and seasonal dynamics and compared the differences between functional groups. Furthermore, one-way analysis of variance was used to analyze the effects of island area on different spider functional groups. The results showed that 3503 spider individuals were collected, including 1438, which were identifiable adults belonging to 30 families and 82 species. Among the identifiable individuals, Spermophora sp. 1, Clubionidae sp. 2, Ctenizidae sp. 2, and Thomisidae sp. 3 accounted for 7.37%, 6.61%, 5.84%, and 5.29%, and Ctenizidae sp. 2 were sampled on all 16 islands. The Shannon-Wiener index revealed that the difference in the spider diversity between the various seasons was significant (P < 0.05). Spiders showed the highest diversity in autumn compared with that in spring and summer. For the functional group structure, the abundance of Ambush predators was the highest, followed by that of Cursorial hunters was, and that of Orb weavers was the lowest. There was a significant difference in individuals between the Burrowing spiders and other functional groups (P < 0.05). The individual Cursorial hunters and Ambush predators were significantly higher than those of Sheet-line and Orb weavers were (P < 0.05). The individuals in the functional group showed significant differences between the small and large islands. The diversity of Ambush predators on small islands was significantly higher than that on the large islands was. The proportion of Sheet-line weavers and Ambush predators on the small islands was significantly lower than that on the large islands was; the proportion of Cursorial hunters on small islands was significantly higher than that on large islands; but for Orb weavers and Burrowing spiders, there was no significant difference between the small and large islands. In conclusion, spider diversity showed seasonal dynamics and, to a certain extent, the habitat fragmentation affected the distribution of different spider functional groups.