The purpose of this study is to explore the relationship between the activity of Lvnonglin^®31 compound microbial agent (LNL31), the occurrence of blister blight and the structure of endophytic bacterial communities in tea, and to provide a theoretical basis for the rational application of microbial agents for green control of blister blight in Camellia sinensis var. assamica. The activity of LNL31 was evaluated through indoor antibacterial spectrum testing, laser confocal microscope morphology observation, pathogenic fungus spore germination inhibition rate test, and transparent circle detection enzyme activity methods. Field randomized block trials were carried out to test the disease prevention and growth promotion effects of LNL31 with different dilution ratios. Then the tea tree bud length, bud density, fresh weight and chlorophyll were respectively measured. Using 16S rDNA sequencing technology, the differences in the occurrence of the blister blight in C. sinensis var. assamica and the community structure of endophytic bacteria in leaves under LNL31 were investigated. The diluted LNL31 had obvious inhibitory effect on five pathogens, such as Exobasidium vexans EV01, Colletotrichum gloeosporioides CG02, Fusarium oxysporum FOC4, Xanthomonas axonopodis pv. citri XC01 and Escherichia coli DH5α, which caused the hyphae to break, expand and digest. The inhibition rate of LNL31 on spore germination of pathogenic fungi EV01, CG02 and FOC4 reached 89.04%-93.00%. In field randomized block trials, the application of 500-fold dilution of LNL31 had the most significant disease prevention and growth promotion effect, which was similar to the treatment of the pyraclostrobin, followed by 1000-fold dilution of LNL31. The averages of bud length, germination density, hundred bud weight and chlorophyll of the plants in the treatment of LNL31 increased by 23.14%-36.17%, 32.10%-51.38%, 27.66%-40.00% and 28.88%-36.14%, respectively, in comparison with the control. After spraying different concentrations of LNL31, the richness and uniformity of endophytic bacterial communities increased, and the results of principal coordinate analysis (PCoA) showed that there was a significant impact on bacterial communities in leaves. At the taxonomic level, Rhizobiales and Sphingomonadales were the dominant bacterial orders; Methylobacterium was the dominant bacterial genus, followed by 1174_901_12, Sphingomonas and Rhizobium. Linear discriminant analysis (LEfSe) showed that there were 9-14 indicator bacterial groups in the treatment sprayed with LNL31, compared with only 7 indicator bacterial genera in the control. Cluster analysis of species abundance showed that the unique dominant genus Baierinkia and Burkholderia in the treatment of LNL31 were similar in abundance, while Rhizobium and 1174_901_1 were similar in abundance. Correlation network analysis Bacillus is positively correlated with Eubacterium and Parabacteroide, and negatively correlated with Methylobacterium, Beijerinckia and Luteibacter. Bugbas's functional prediction showed that the abundance of aerobic bacteria, biofilm forming, gram-negative bacteria, stress-tolerant bacteria, movable elements, and facultative anaerobic bacteria treated by the composite microbial agent increased by 3.24%-14.78%, and potential pathogenic bacteria dropped by 5.70%. LNL31 showed a good effect of preventing diseases and promoting growth, and significantly changed the community structure and functional characteristics of endophytic bacteria in tea, enabling a few disease-resistant related species to grow in an advantageous way, which provided a basis for biological control of blister blight of tea.