Objective To investigate a foodborne illness outbreak in S restaurant and identify the pathogenic factors in order to prevent the occurrence of similar incidents. Methods According to established case definition, active case search and interview was implemented. Descriptive epidemiology was used to address epidemiologic characteristics, case-control study was conducted to analyze the risk factors, and samples were collected for testing as well. Results 162 cases was identified from the banquets, with the attack rate of 22.2% (162/730). The major clinic symptoms were diarrhea (100%, 162/162), stomachache (96.3%, 156/162), asthenia (77.2%, 125/162), nausea (68.5%, 111/162) and vomiting (53.1%, 86/162). The average incubation period was 12 hours. According to the result of case-control study, eating scallop (OR=1.74,5%CI:1.00-3.02) and calf ribs (OR=2.87,5%CI:1.38-5.99) was a risk factor. Samples from 34 patients, turtle pieces and cutting board were tested positive for Vibrio parahaemolyticus. Conclusion The main cause of this foodborne illness outbreak accident was due to Vibrio parahaemolyticus contamination, combined with cross contamination and undercooked food. It was necessary to standardize the operation procedures, strengthen the self-regulation of restaurants and consciousness to prevent such cases.