Objective To find out the causes of food poisoning in a school banquet and identify the pathogenic bacteria, so as to provide evidence for the treatment of food poisoning. Methods A field epidemiological survey was conducted to search for cases, find suspicious poisoning meals and food, and collect cases and food samples for laboratory testing, to determine pathogenic pathogens and virulence genes. The pulsed field gel electrophoresis (PFGE) was applied to identify the homology of the pathogens. Results A total of 92 poisoning cases were found, and the incidence rate was 46.94%. The main clinical manifestations were diarrhea (93.48%), abdominal pain (86.96%), nausea (39.13%), vomiting (34.78%) and fever (17.39%). The median of onset latency was 17 hours. Vibrio parahaemolyticus was detected in samples from 3 patients (2 stools and 1 anal swab). The virulence gene trh was positive and the similarity coefficient of PFGE banding was 97.4%. Pathogenic bacteria were not detected in 10 food samples. The results of the case-control study showed that six types of food were suspicious (OR values were 15.75, 10.14, 8.44, 5.93, 5.56 and 4.71 respectively, P<0.05 and OR 95%CI>1), including couple lung slices and California bass with extremely high risk of exposure (OR values>10). Conclusion 　The food poisoning resulted from this enrollment banquet was caused by trh-positive Vibrio parahaemolyticus and no suspicious food was identified (the possibility of contamination by couples^' lung slices and California sea bass was high). It is suggested that the supervision and management of catering units and food safety publicity and education should be strengthened to reduce the occurrence of food-borne diseases from the source.