Objective To find out the suspicious food, pathogenic factors and risk factors of a foodborne disease outbreak in a factory, and to discuss the problems exposed in the investigation of the incident, so as to provide reference for the prevention, control and investigation of similar incidents in the future. Methods A case was defined as the onset of abdominal pain or diarrhea(≥3 times/24 hours)or vomiting in a person who worked in M factory from March 3 to March 4 in 2019. Case interviews and retrospective research was carried out using descriptive and analytical epidemics pathological method. Stool specimens of the cases,leftover food and related environmental samples were gathered for pathogen isolation and toxin gene detection using polymerase chain reaction(PCR). Results 106 cases were identified with a attack rate of 73.6% (106/144). The symptoms were diarrhea (78.3%,83/106), abdominal cramps (78.3%,83/106), abdominal gas pains(9.4%,10/106),and no fever. The epidemic curve showed a point source exposure pattern. The median incubation time was 10 hours (range:2-22 h). Illness were associated with three food items of the lunch on March 3 in 2019 by univariate analysis and Logistic regression analysis:braised fish pieces [relative risk (RR)=1.55,95% confidence interval (95%CI):1.29-1.85], pork stir-fried with garlic sprouts (RR=1.26,95%CI:1.01-1.57) and duck blood stir-fried with pickles (RR=1.47,95%CI:1.16-1.87). Alpha toxin and enterotoxin CPE genes were positive and beta toxin genes was negative in the Clostridium perfringens strain isolated in anal swabs of three patients, three environmental samples and two leftover food samples. There were possible bacterial contamination and reproduction in the processing and preparation of enterprise D, which delivered food. Conclusion This incident was caused by the food poisoning of Clostridium perfringens caused by the consumption of a meal provided by a catering company. After the meal was delivered, it should be cooled quickly and stored at low temperature. If it cannot be eaten immediately, it should be heated sufficiently before eating.