To investigate the reason of a food poisoning case, and the origins of the suspicious factors of this case.MethodsFind out the suspicious meal according to the epidemiological curve. Then evaluate the foods in the suspicious meal through case-control study, and analyze the correlations between different foods and different dozes. Foods and case samples were collected for laboratory testing.Results 61cases were founded and the major symptoms were abdominal pains (98%), diarrhea(90%), nauseous(54%) and so on. Eating plain chicken was the risk factor (OR=9.25,95%CI∶1.14-200.07), and showed a dose-effect relation (χ^2test for trends:25.71,P<0.01). The main reason for cross contamination was that the chef processed the plain chicken and Tilapia at the same time. Vibrio parahaemolyticus was detected in the anus swab samples from patients, the result of PFGE showed 100% homology.ConclusionThe food poisoning was caused by plain chicken contaminated by Vibrio parahemolyticus. It is necessary to strengthen the supervision and administration of catering distribution, and improve health consciousness of the public to prevent such case.