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A new kind of postharvest rot on Chinese cabbage (Brassica rapa L. ssp. pekinensis) caused by a fungus was observed in vegetable cellars in Harbin, China in 2019 and 2020, causing considerable economic losses. A water-soaked spot appeared at the base of the midrib of leaves, extended into the upper part of the midrib, and ultimately turned into rot. The diseased part was dark brown or black with a few black spores on the surface. Fungal isolates were obtained from the diseased plants and identified as Aspergillus welwitschiae through morphological observation and multigene sequencing analysis of the internal transcribed spacer, β-tubulin and calmodulin genetic regions. Pathogenicity tests were conducted, and the resulting symptoms on Chinese cabbage were similar to those seen in the vegetable cellar. The isolates were also associated with rot and leaf spot on seedlings and affected the seed germination of Chinese cabbage. A host range test showed that the isolates could infect some common vegetables, including carrot, kidney bean, broccoli, radish, Chinese flowering cabbage, root-mustard, cabbage, non-heading Chinese cabbage, pepper, lettuce, oilseed rape, tomato and cucumber. The isolation, identification, and host range of the pathogen can provide a basis for the study of the occurrence, prevention and management of the disease in the future. [ABSTRACT FROM AUTHOR]