In the spring of 2020, the typical diseased citrus fruits were collected in Changshou, Chongqing, and the blight fruits of dayagan(Citrus reticulate cv. dayagan) were obtained. The strain CS11 was obtained from the diseased samples by tissue separation. Through morphology and molecular biology characterization, strain CS11 was determined as Stagonosporopsis cucurbitacearum(S. ucurbitacearum). Pathogenicity study by spraying the spores on health citrus plants showed that strain CS11 caused blight on citrus, which confirmed the pathogenicity of strain CS11. S. ucurbitacearum strain CS11 has pathogenicity on Citrus reticulate cv. Dayagan, C. rtemple×Dancy, C. sinensis (L.) Osbeck (Tarocoo blood orange) and C. limon. And the strain CS11 is pathogenic to the leaves, branches and fruits of the 4 kinds of citrus. The growth rate method was used to determine the virulence of different agents to the strain, the results showed five fungicides including 75% trifloxystrobin tebuconazole, 60% pyraclostrobin metiram, 450 g/L prochloraz, 37% difenoconazole and 11.5% pyraclostrobin had good inhibitory effect on strain CS11. The EC50 values of 75% trifloxystrobin tebuconazole, 60% pyraclostrobin metiram, 37% difenoconazole and 11.5% pyraclostrobin were all less than 10 mg/kg.