Abstract: The sore mouth disease is one of the common diseases in sheep breeding in Pingnan County, which has restricted the healthy development of sheep breeding industry in Pingnan County. By determining the pathogen of clinical sore mouth disease in Pingnan County and understanding the prevalence of the disease in Pingnan County, it would provide a basis for the scientific prevention and treatment of the disease. PCR was used to detect the pathogens of 12 cases of clinical sore mouth disease in the county, and a total of 217 sheep blood samples were randomly collected from 6 large-scale sheep farms (households) in the county for epidemiological investigation. The results showed that the DNA samples of viral genome extracted from the pathological tissue and blood samples of the 12 cases were amplified to approximately 500 bp fragments, which were consistent with the expected fragment size, so it was identified that the pathogen causing clinical sore mouth disease in Pingnan County was ORFV. The infection rate of ORFV in 6 large-scale sheep farms (households) in Pingnan County was 14.63%-33.33%, with an average infection rate of 25.99%. Among the sampled groups, all the sheep with clinical symptoms of sore mouth disease were 1-3 month-old lambs, and the clinical incidence rate of each farm was 0-16.33%, with an average incidence rate of 9.69%, which was lower than the infection rate of ORFV.