Objective: To explore the diversity and variability of symbiotic microbial communities in Culicoides on different livestock farms in Hainan Province, China. Methods: From August to September 2021, the ultraviolet lamp-trap method was used to collect Culicoides on five different livestock farms (cattle farms, chicken houses, dog houses, sheep pens, and pigsties) in Wenchang City, Ding'an County, and Ledong County in Hainan Province. After the total DNA was extracted by hexadecyltrimethylammonium bromide method, the structural characteristics and functional distribution of genes in the microbial communities were analyzed using metagenomic sequencing. Results: The dominant species of Culicoides on different livestock farms varied. The dominant species on cattle farms, sheep pens, and pigsties was C. oxystoma, accounting for 92.91%, 82.22%, and 95.85%, respectively; the dominant species in chicken houses and dog houses were C. arakawae, accounting for 66.36% and 98.22%, respectively. On different livestock farms, Proteobacteria (33.78%), Ascomycota (9.09%), and Firmicutes (8.88%) were the dominant phyla of the symbiotic microbial communities in Culicoides, and Acinetobacter (22.48%) and Clostridium (7.25%) were the dominant genera. Microbial diversity analysis at the genus level found that the five livestock farms shared the most microorganisms at the genus level, with 3 357 genera in common. Microbial gene differential analysis revealed that the five livestock farms shared a relatively small number of common genes (1 065). Moreover, the functional prediction results also showed that 29.10% of the annotated genes were related to metabolism, such as carbohydrate metabolism, amino acid metabolism, and lipid metabolism. The analysis of the differences in gene number showed that increased similarity in the species composition of Culicoides was associated with a greater number of genes shared by the samples. Conclusions: Analysis of the microbial communities found that the core symbiotic microflora communities in Culicoides is relatively stable, and livestock farms with the same dominant species of Culicoides have more similarities in microbial communities in Culicoides. This study enriches the microbial community database of Culicoides in China, which is of great significance for the biological prevention and control of Culicoides in the future.