Objective To Investigate the cause of a food poisoning incident in a city in Dehong Prefecture， determine the scope of the incident， and to formulate effective prevention and control measures. Methods Field epidemiology and case-control study methods were used to formulate case definition； carry out case search； find suspicious food combined with clinical manifestations， dining history and other information； and collect samples from the suspicious food， cases and environment for laboratory testing. Results A total of 160 cases were found and the incidence rate was 26.02% （160/615）. The main clinical manifestations were diarrhea， leukocytosis， vomiting， nausea and abdominal pain. The average incubation period was 10.89±5.09 h， with 2 h as the shortest and 28 h as the longest. The epidemiological curve suggested the point source exposure mode. The results of case-control study showed that eating roast pork with green shoots was an independent risk factor （OR=13.09， 95%CI： 3.26‒52.54）.16 samples were tested by the local CDC laboratory. Proteus mirabilis was detected in two the anal swabs of two patients He and Chen. Both proteus pani and proteus mirabilis were detected in anal swab of patient Zhou and Proteus pani was detected in roast meat. There was no detection of pathogenic bacteria in other samples. Conclusion Based on the field epidemiological investigation and laboratory test results， we conclude that the food poisoning incident is caused by suspected proteus bacteria. We suggest that the market supervision department should strengthen the supervision of local food hygiene； clarify the sampling rights， responsibilities and technical procedures when medical institutions treat patients with foodborne diseases； ensure finding the causes in time； and take effective prevention and control measures to avoid similar food poisoning events.