Abstract: A pathogen causing leaf black spot of medicinal Chrysanthemum morifolium‘Huaihuang’was isolated and characterized based on the morphological features，phenotypic analysis of spore production，pathogenicity test，and sequence analysis of internal transcribed spacer region of the ribosomal DNA（rDNA-ITS）. The results showed that the black spot disease was caused by Alternaria sp. A1 and A2，two pathogenic strains，were obtained from the diseased plants. Although isolates A1 and A2 showed some variations on colony texture，color，edge uniformity，and sporulation phenotype，there was no significant difference in their pathogenicity to Chrysanthemum morifolium‘Huaihuang’leaves. The rDNA-ITS sequence of the two fungi strain showed 100% identity. The sequence of the identified fungus has been submitted to GenBank（GenBank accession number：KF688111）.

Key words: Chrysanthemum morifolium‘Huaihuang’, black spot disease, pathogen identification