Abstract: A bacterial strain was isolated from the lungs of weaned pigs in the infected intensive pig farm in Fujian Province. According to the morphological observation, biochemical test, cultural characteristics, PCR identification and animal challenge test of the isolated bacteria, and combined with the clinical symptoms and pathological changes of the infected pigs, it was indicated that the isolated bacteria was partial to anaerobic Streptococcus, which had the characteristics of good culture on blood plate and could cause the disease and death of mice. The drug sensitivity test showed that the isolated Streptococcus was highly sensitive to vancomycin, imipenem, linezolid and rocephin, and was moderately sensitive to amoxicillin, florfenicol, cefotaxime, macrodantin and tigecycline, while was not sensitive to the drugs such as cardoxycycline, polymyxin, penicillin, streptomycin, and enrofloxacin. According to the results of drug sensitivity, the pig farm should take emergency prevention and control measures, and the epidemic could be effectively controlled 5 days later.