Objective To investigate a food poisoning events occurred in multiple schools at the same time,and analyze pathogenic factor, contaminated food and source, in order to guide clinical treatment and preventive measures. Methods Based on the investigation of clinical characteristics and epidemiological distribution of patients, homology analysis of Salmonella from different sources was carried out with the combination of pulsed field gel electrophoresis(PFGE) in the laboratory. Results Totally 37 suspected cases were found from 4 school in different districts, 19 cases were diagnosed. The main clinical features of the patients were diarrhea (70.27%, 26/37), fever (54.05%,20/37), abdominal pain (51.35%,19/37) and vomiting (37.84%,17/37). A total of 24 strains of Salmonella Enteritidis were isolated in the laboratory, of which 19 strains were from cases and 5 strains were from sandwiches and their dried meat floss. According to PFGE, 24 strains of Salmonella Enteritidis were clustered to 100.00%. The drug resistance rate of 19 cases was 100.00% to nalidixic acid and 5.26%(1/19) to cefoxitin and imipenem. Conclusion Combined with the clinical feature, epidemiological investigation and laboratory test results, it was confirmed that the main cause of the incident was the raw material of the sandwich which was contaminated by Salmonella Enteritidis. It is suggested that the regulatory department should strengthen the supervision of the school catering company, improve the food safety awareness and prevent the foodborne disease.