This study applied cluster analysis and MDS sequence analysis to catch-rate data of fish species from bottom-trawl surveys in the Bohai Sea in August of 2012 to 2016. We selected keystone species of the fish community in the Bohai Sea, based on the annual contributions of similar species within clusters and different species between various clusters. (1) When the similarity contribution rate ranged from 29.93% to 35.69%, the fish communities in the Bohai Sea were clustered into 7, 9, 6, 5 and 6 groups for 2012-2016 consecutively, with corresponding MDS coefficients equaling 0.16, 0.14, 0.18, 0.15, and 0.17 respectively. (2) There were significant differences (=0.001) in the species composition of the fish community groups among the five years. The fish species were identified for each year that had cumulatively contributed to about 80% of the difference between community groups and occurred in more than half of the groups. Unfortunately, no common species was identified for all five years. was identified in three years. For species which contributed to more than 10% of the between-groups difference and displayed a more than 50% of occurrence in a year, none occurred in four or five years, only occurred in three years. (3) Similarly, the fish species were identified for each year that had cumulatively contributed to about 80% of the difference within groups and occurred in more than half of the groups. No species were common to three or more years. Three species (i.e. Synechogobius hasta) occurred in two of the five years. For species which had contributed to more than 10% of the within-groups difference and displayed greater than 50% occurrence in a year, no species occurred in more than four years, only Chaeturichthys stigmatias and occurred in two years. (4) Based on the annual cumulative or single similarity or difference contribution rates of every fish species to community groups, we conclude that is the primary keystone species in the fish community structure of the Bohai Sea, the Chaeturichthys stigmatias and . This conclusion is supported by the ratio, correlation, and regression of the average catches per station of these four species to that of all the pelagic or demersal species, and the annual dominance indices of these species. Results of this study provide a scientific basis for the adjustment of the fishing industry and the maintenance of fishery resources in the Bohai Sea.