The wet heartwood and normal wood of 6-year-old Populus deltoides Bartr. ‘Huashi2’ in the Jianghan Plain were used to study the role of bacterial and microbial communities in the pathogenesis in the wet heartwood of Populus. High-throughput sequencing was used to sequence the V5-V7 region of the 16S rRNA gene. The results of sequencing were analyzed with bioinformatics. Methods including principal component analysis， α-diversity index analysis， and microbial network analysis were used to study the differences in the structure and composition of the bacterial and microbial communities in the wet heartwood and normal wood of 6-year-old Populus deltoides Bartr. The results of principal component analysis showed that the bacterial abundance of the genera Ralstonia and Bacteroides was the highest， while the proportion of the genera Bacteroides， Pleomorphomonas and Hydrogenispora in wet heartwood was significantly higher than that in normal wood （P<0.05） at the genus level of the bacterial and microbial communities in the wet heartwood and normal wood of 6-year-old Populus deltoides Bartr. The results of analyzing the functions of microbial communities showed that Ralstonia were mostly phytopathogenic bacteria， which widely existed in wet heartwood. The results of analyzing the alpha diversity index showed that the diversity and species distribution uniformity of the community in the wet heartwood were higher than those in the normal wood， and the total number of species in the wet heartwood was lower than that in the normal wood. The results of analyzing the co-occurrence network showed that there was a lot of competition and antagonism between bacteria and microorganisms in the normal wood of Populus deltoides Bartr， and the community was relatively unstable. There were more synergistic and mutualistic relationships among bacteria in wet heartwood， and the microbial community was relatively stable. The results of analyzing key microorganisms showed that the key bacterial microorganisms in the wet heartwood of 6-year-old Populus deltoides Bartr. were Aquabacterium， WCHB1-32， etc.， and the key bacterial microorganisms in the normal heartwood of 6-year-old Populus deltoides Bartr. were Pleomorphomonas， Dysgonomonas， etc. These key microorganisms played an important role in stabilizing the structure of microbial network in the wet heartwood. It is indicated that the formation of wet heartwood in Populus deltoides Bartr. is affected by multiple factors and is the result of the joint action of microbial communities.