Abstract: Objective This investigation was designed to well understand the outbreak epidemic occurring in Jianshan Weikeng Development Area of Haining Municipality and the cause．Methods Field epidemiological survey was conducted and analysis Was made on the epidemic situation．Common pathogenic bacteria were isolated according to GB4789-1994．Slide agglutination test was used for serological identification，VITEK32 for biochemistry identification，PCR for detecting the virulence genes，and the improved K-B method for drug sensitivity of isolates．Results Field epidemiological survey showed that the outbreak epidemic were associated with poor basic sanitary facilities like tap water system and W.C in the newly established development area．Laboratory study detected 9 strains of Shigella flexneri 4c in feces of 59 patients，the positive detection rate being 15.25％．All the strains bore virulence gene and had similar sensitivity and resistance to drugs．Conclusion The outbreak epidemic is caused by shigella flexneri 4c，which is reported for the first time in our province. Drugs such as CF、AKN、FPA、CIPX ale effective for the treatment dysentery caused by this strain of bacterium．