, one of the important sources of agar, is the third most widely cultivated seaweed in China, after . In recent years, there has been a large-scale decrease in the cultivation of , resulting in huge economic losses for the seaweed cultivation industry. Epiphytes grow as an integral part on the surfaces of large algae, and the variations in the seaweed-associated microbial community compositions are typically associated with disease occurrence. In this study, the 07-2 strain was used as experimental material. DNA of epiphytes from the healthy, adjacent, and bleached fronds was extracted, and the V3 variables amplified from 16S rDNA genes were carried out by denaturing gradient gel electrophoresis (DGGE). Finally, the 23 objective bands were cloned and identified. The number and diversity index of the bacterial community of the epiphytes from the three fronds were calculated after digitization of the experimental results. The similarity among the dominant species in the bacterial communities were compared by non-metric multidimensional scaling (nMDS) and redundancy analysis (RDA). The results show that the colony forming units and bacterial community diversity increased gradually with the aggravation in the degree of lesion in <0.05). The nMDS results indicate that the bacterial community composition of the epiphytes varies between the healthy and bleached fronds, while the composition of adjacent fronds is closer compared with that between healthy fronds. The RDA results reveal that the potential dominant bacteria of the epiphytes of the healthy and adjacent fronds are Pseudoalteromonas, respectively. However, the potential dominant bacteria of the epiphytes of the bleached fronds were not identified. The dominant bacteria of the epiphytes of the bleached attached fronds were . It can be seen from the above results that there is a significant difference between the healthy fronds and the diseased fronds of in terms of the bacterial community composition and dominant bacteria of the epiphytes, while the epiphytic bacterial community composition of the adjacent fronds was more similar than that of the healthy fronds.