Abstract: In order to clarify the pathogen species causing the potato blackleg disease in winter-planting potatoes in Xiapu County and screen the efficient and safe seed dressing agents, providing a technical basis for the scientific prevention and control of local potato blackleg disease, the systematic field sampling was conducted on the infected potato plants with blackleg symptoms in Xiapu County from 2023 to 2024. The pathogen isolation and purification were performed by using the tissue separation methods, followed by the pathogen identification through pathogenicity tests and 16S rDNA sequence analysis. Concurrently, during the production season of 2024−2025, the field efficacy trials were carried out. By taking Minshu No.1 as the test material, the seed dressing treatments with 3% zhongshengmycin (T1), 46% copper hydroxide (T2), 2% kasugamycin (T3), 20% thiodiazole copper (T4), 2×10⁹ CFU·g⁻¹ bacillus subtilis (T5), 5×10⁹ CFU·g⁻¹ Bacillus amyloliquefaciens (T6) and distilled water as the control (CK) were set up to compare the effects of each treatment on the control effect, yield and commodity potato rate of potato blackleg disease. The results showed that the typical symptoms of potato blackleg disease included leaf yellowing, curling and dark brown discoloration at the stem base. The pathogen formed milky white colonies, which were circular or nearly circular. The results of pathogen identification showed that the blackleg disease of winter-planting potato in Xiapu County was caused by the composite infection of Pectobacterium carotovorum, Pectobacterium atrosepticum, Pectobacterium brasiliense and Pectobacterium polaris, among which Pectobacterium brasiliense was the dominant species. The field experiments showed that the seedling emergence rate of each seed dressing treatment was higher than that of CK (89.60%), ranging from 93.57% to 97.21%. At the full seedling stage and budding stage, T6 exhibited the best control efficacy (70.15% and 67.19%, respectively), followed by T5 (65.67% and 65.17%, respectively). In terms of yield, T6 achieved the highest yield (38471.25 kg·hm⁻²), representing a 38.54% increase compared to CK, with a marketable tuber rate of 91.70%. T5 ranked second with a yield of 37698.97 kg·hm⁻², a 35.76% increase over CK, and a marketable tuber rate of 89.77%, which were significantly better than those of CK and other chemical treatments. The seed dressing treatment with 5×10⁹ CFU·g⁻¹ Bacillus amyloliquefaciens and 2×10⁹ CFU·g⁻¹ Bacillus subtilis showed excellent efficacy against potato blackleg disease, significantly improving the seedling emergence rate, yield and commodity potato rate, which could be popularized and applied in production.