Abstract: In order to make clear species of the pathogen of buckwheat ring rot in Yunnan Province, the occurrence and damage of buckwheat ring rot were investigated, and the diseased leaves were collected in buckwheat planting base in Yunnan. The pathogen of buckwheat ring rot were isolated and cultured by using tissue dissociation method, and the pathogen was identified through microscope and molecular identification method. The results indicated that the pycnidia were spherical or flat spherical, brown. The conidia were single cell, hyaline, oval or short rod-shaped. The rDNA ITS region of the pathogen were PCR-amplified with fungal universal primers and sequenced，and the sequences of ten strains showed 99% homogeneity with those of Phoma herbarum. Based on morphology and rDNA ITS region sequences analysis, the pathogen of buckwheat ring rot in Yunnan was identified as Phoma herbarum.