Laizhou Bay is located in the southern part of the Bohai Sea, and is one of three major bays in the Bohai Sea. Laizhou Bay contains many species of crabs and is an important spawning and feeding ground for commercial crab species such as Portunus trituberculatus and Charybdis japonica. In recent years, the ecosystems and marine living resources in Laizhou Bay have been greatly affected due to the overexploitation of fisheries. Compared to the severe decline of economic fish resources, the decline in crab resources has been relatively slow, and the importance of these crabs in the ecosystem has been gradually increasing. Investigating the interannual variation of crab community structure and its influencing factors in Laizhou Bay provides a scientific basis for the rational utilization of crab resources. This study reports on the interannual variation and influencing factors of the summertime crab community structure in Laizhou Bay, based on bottom-trawl survey data from 2010 to 2019. This includes a description of the species composition, dominant species, biodiversity indices, community structure, and environmental factors affecting crab communities. Of the 16 crab species reported from this area during summer from 2010–2019, 14 occurred in 2011, although this reduced to seven in 2017; there were two to four dominant species per year. The average number of crab species decreased by 0.31 each year; the biomass and mantissa of crabs had initially decreased, then increased. Charybdis japonica and Portunus trituberculatus are the important dominant species in Laizhou Bay, the former being the first dominant species in 10 y and the latter being the dominant species in 8 y. The crab diversity index decreased significantly from 2014 to 2015. Crab assemblages in different years were divided into four groups: A (2010), B (2011, 2014, 2015), C (2012, 2013, 2018, 2019), and D (2016, 2017). The permutational multivariate analysis of variance test demonstrated that the crab community structure significantly differed between the four groups. The similarity percentages breakdown (SIMPER) analysis showed that characteristic species for different community groups were Charybdis japonica, Portunus trituberculatus, and Philyra carinata. The average dissimilarity between groups A and D was the largest (48.45%), and the main discriminating species were Dorippe japonica, Charybdis japonica, and Eucrate crenata. The average dissimilarity between groups A and B was 38.1%, and the main discriminating species were Dorippe japonica, Eucrate crenata, and Hemigrapsus penicillatus. Other discriminating species for different community groups were Heikeopsis japonicus, Raphidopus ciliatus, and Philyra carinata. Redundancy analysis showed that bottom sea chlorophyll, benthos biomass, and the Oceanic Ni?o Index were the key environmental factors affecting the interannual variation of crab community structure. The crab community structure was greatly affected by petroleum in 2011, as a result of the Penglai 19-3 oil spill accident. The strong El Nino event had a significant impact on crab community structure in 2014 and 2015, leading to a significant decrease in crab biomass and biodiversity in Laizhou Bay.