Abstract: In order to identify the pathogenic fungi causing Bletilla striata cultivation disease in the planting base of Nanning, Guangxi, and screen for highly effective fungicides, this study collected typical samples of leaf spot disease. The pathogenic fungi were isolated and purified, and the pathogenicity of the isolated strains was verified according to Koch's postulates. The identification of the pathogenic fungi species was performed through a combined analysis of morphological characteristics and multi-gene sequencing. The inhibitory effects of 10 fungicides on representative strains were determined using the mycelial growth rate method. The results showed that the isolated pathogenic fungi causing B. striata leaf spot disease were identified as Alternaria alternata, a species of chain spot fungus. Inoculating the pathogenic fungi onto healthy B. striata leaf samples resulted in disease symptoms similar to those observed in the field. Among the tested fungicides, oxathiapiprolin exhibited the strongest inhibition activity against the mycelial growth of this fungus, with an EC₅₀ value of 1.25 μg/mL. The findings of this study provide scientific evidence for the identification and control of B. striata leaf spot disease.