The coastal waters along the southern Shandong Peninsula waters are rich in fishery resources, and the spawning and feeding grounds for many important economic marine organisms are located here. In recent years, overfishing and pollution have caused considerable damage to fishery resources here, and crabs, including important economic species (such as ) and bait-type species (such as ) have been adversely affected. Although the community structure and diversity of crabs are of great significance for fishery production and fishery ecology, little research has been conducted in this respect in the southern Shandong Peninsula waters. Based on data from four bottom trawl surveys in this area from 2014 to 2015, the spatial and temporal distribution, structure community, dominant species, and diversity of crab populations were analyzed. Fifteen species of crabs were caught during the four surveys, which belonged to 7 families and 12 genera. The number of species caught changed seasonally because, as the area is located in the warm temperate zone, its temperature changes seasonally and the migratory crabs migrate to and from this area seasonally as well. were the main economic species caught, and the others were low-value species. Because of the reduction in the number of natural enemies, the euryhaline was the dominant species in all four surveys. Biomass changed seasonally, with the highest biomass observed in summer and the lowest in winter. Except in autumn, distribution of biomass differed regionally owing to the migration and foraging of . According to the data, the range of the Shannon-Wiener diversity index (') was 0.23-0.37, and that of the Margalef richness index () was 0.32-0.55. The diversity index changed seasonally, indicating an unstable community structure and lower-level diversity of crab populations in this area. The diversity index was higher in the east, lower in the west, and higher in the near shore, and lower in the offshore; therefore, we conclude that the eastern offshore area along the southern Shandong Peninsula is suitable for crab growth. The results of a CLUSTER analysis showed that the crab species in every season in the coastal waters along the southern Shandong Peninsula could be divided into three groups:the southwestern waters group, the northeast waters group, and the northwest waters group. The populations in every group changed with season and the community structure was unstable. The key factor that influenced groups division was the presence of small bait-type species, such as , because the populations of the large economic species are facing considerable damage due to overfishing and environmental pollution. This study shows that:1) Mostcrabs in the coastal waters along the southern Shandong Peninsula were small, bait-type species. The crab diversity was very low, and the dominant species varied considerably. 2) The community structure of crabs in the coastal waters along the southern Shandong Peninsula can be divided into three parts; most of the crabs found in this area are small bait-type crabs.