Abstract: Objective This epidemiological investigation was conducted to identify the cause of a bacillary dysentery outbreak and to provide evidence for the development of responding measures. Methods Case investigations were conducted based on definite identification of suspected cases, probable cases, clinically diagnosed cases and confirmed cases to outline the time, regional and population distribution. Hygienic surveys were conducted in epidemic areas to uncover the cause of the outbreak. Results A total of 111 cases were identified, the attack rate being 3.50%. Drinking raw water was found to be the main risk factor. Conclusion The bacillary dysentery outbreak was caused by food-borne and water-borne Shigella flexneri 2a. Such insalubrious lifestyles as drink unsterilized water of the Dong Ethnic people were the major contributory factors.