To identify the cause of poisoning, take effective intervention promptly and to provide scientific evidence to prevent and control similar epidemic diseases in the future.Methods Cases were screened by verifying diagnosis, interviewing and searching in the company. Exposure patterns and factors were identified by applying descriptive epidemiology. The corelation between the factors and diseases was analyzed through retrospective cohort study. Samples of feces, vomitus and food remains were detected.Results Retrospective cohort study indicated fried squid with green peppers and tofu roll salad for lunch on 18^th were suspicious for the 37 cases. Vibrio parahaemolyticus were found in both feces and food remains.Conclusion The outbreak was caused by squid contaminated by Vibrio parahaemolyticus and cross contamincation occured in the process of making tofu without adequate sterilization treatment.