Objective: This study focused on the effectively control of the spoilage and deterioration of grouper during refrigeration. Methods: Illumina high-throughput sequencing technology was used to amplify the 16S rDNA V3-V4 segment of bacteria, then analyzed the changes in the bacterial community structure of E. obliquus after being treated with 400 MPa UHP for 5 minutes and refrigerated at 4 ℃ for 3, 6, 9, and 12 d. Results: According to Alpha diversity analysis fish samples treated with and without UHP showed increasing Chao1 and Ace indices as refrigeration times were extended, but Shannon indices progressively dropped. Nonetheless, the fish samples treated with UHP had lower Chao1, Ace, and Shannon indices than the ones not treated with UHP at every refrigeration stage (3~12 days). Analysis of microbial community structure showed there was a difference in the changes in microbial community structure during the refrigeration process of the two types of fish samples. During the refrigeration period, the main dominant microbial communities in fish samples without UHP were Streptococcus (17.70%, 3 d), Plesiomonas (36.66%, 6 d)， and Peptostreptococcus (67.65%, 9 d; 43.4%, 12 d), while the main dominant microbial communities in fish samples treated with UHP were unclassified Enterobacteriaceae (27.36%, 3 d), Plesiomonas (40.31%, 6 d), Lactococcus (24.45%, 9 d), and Peptostreptococcus (77.91%, 12 d). Meanwhile, Peptostreptococcus was identified as the specific dominant bacteria for the later stage of cold storage (12th day) of two processed fish samples. PICRUSt functional gene prediction found that the relative abundance of genes related to stress response, toxin transport, DNA recombination, and signal transduction in fish samples treated with and without UHP increased significantly on the 9th and 12th days of refrigeration, respectively. Conclusion: Compared with the samples without UHP, UHP treatment can effectively reduce the abundance and diversity of bacterial communities, change the succession pattern of the main dominant bacterial communities, and affect the abundance structure changes of the bacterial communities in the fish samples during refrigeration.