Abstract: The influences of salinity on bacterial communities in a coastal area of Yuniao River in the Muping District of Yantai City, China, were analyzed by high-throughput sequencing of in situ and simulation experiments. Proteobacteria, Bacteroidetes, and Cyanobacteria were shown to have a high relative abundance in the community compositions of bacterioplankton and attached bacteria in situ. Proteobacteria occupied the highest relative abundance among all samples, while Cyanobacteria with the second highest relative abundance was inversely proportional to salinity levels in Yuniao River. Among the bacterioplankton community, ammonia-oxidizing bacteriaNitrosomonas and halophile Candidatus Nitrotoga, that have important roles in the nitrogen cycle, were with high abundance. Among the attached bacteria community, salt-tolerant bacteria Porphyrobacter had a high relative abundance that changed according to the abundance of cyanobacteria. Similar results for dominant bacterial communities in different salinities were observed in the simulation experiment. Bacteroidetes and Cyanobacteria had high relative abundance in the simulation experiment, and salinity influenced the diversity and richness of the bacterial community. This was verified by correlation analysis and principal component plot analysis. These findings could provide information and data support for the understanding of the effects of salinity on bacterial communities in coastal areas and the application of salt-tolerant bacteria.