Citrus reticulata cv. Gonggan in Deqing is a national geographical indication product of China, and its quality formation is intricately linked to microbial ecology. In-depth exploration of the microbial resources associated with Gonggan is of great significance for enhancing the quality and increasing the yield of this fruit. [Objective] To isolate and culture bacteria from the rhizosphere soil and phyllosphere surface of Gonggan in Deqing and systematically evaluate their plant growth-promoting functions, thus providing applicable bacterial resources for the eco-friendly cultivation of Gonggan in Deqing. [Methods] Samples of rhizosphere soil and leaves of Gonggan in Deqing were collected. Bacteria within the samples were isolated via the dilution plating method. Bacterial strains were identified based on the homology of their 16S rRNA gene sequences. The functional media for phosphate solubilization, potassium release, nitrogen fixation, and siderophore production were used to evaluate the plant growth-promoting ability of bacterial strains, and the strains with strong plant growth-promoting functions were screened out. Ultimately, pot experiments were conducted to validate the plant growth-promoting functions of the selected strains. [Results] A total of 240 bacterial isolates were obtained, including 96 strains from the rhizosphere soil and 144 strains from the phyllosphere. These strains belonged to 51 genera, 29 families of 4 phyla, where Pseudomonadota was the dominant phylum and Bacillaceae was the dominant family. Functional characterization revealed that 230 (95.83%) strains exhibited at least one plant growth-promoting function, while 123 strains (51.25%) possessed three or more such functions. Given the extended growth cycle of Gonggan in Deqing, we utilized tomato as a model plant to evaluate the plant growth-promoting functions of eight bacterial strains possessing at least two functions through pot experiments. The results demonstrated that the tested strains significantly increased both plant height and fresh weight of tomato plants. [Conclusion] The rhizosphere soil and phyllosphere of Gonggan in Deqing harbor abundant functional microbial resources. This study successfully screened multiple strains of plant growth-promoting bacteria, and pot experiments demonstrated their significant ability to promote tomato growth. These findings provide a solid theoretical foundation for exploiting microbial resources of Gonggan in Deqing and advancing eco-friendly cultivation practices.