Objective Epidemiological investigation of a foodborne disease outbreak triggered by Clostridium perfringens in a school in Guiyang， traceability analysis of etiologic foods and pathogens， and exploration of the application of the new technology of whole genome sequencing in the traceability of foodborne disease outbreaks.Methods On-site epidemiological analysis was used to collect samples of suspected organisms， food samples and samples from the external environment for Salmonella， diarrhea-causing Escherichia coli， Staphylococcus aureus， Bacillus cereus， and Clostridium perfringens for routine laboratory pathogen isolation and identification， and isolates of pathogens for toxin gene detection and whole-genome sequencing traceability analyses.Results Symptoms in 22 cases were dominated by abdominal pain （95.45%， 21/22）， diarrhea （95.45%， 21/22）； the epidemiological profile was point source exposure pattern with an incubation period of 6 h to 15 h. Clostridium perfringens was isolated from 5 anal swabs， 3 stool specimens and 1 retained sample of breakfast meat froth food， and the enterotoxin cpe gene was detected in all of them； Salmonella， diarrhea-causing Escherichia coli， Staphylococcus aureus， and Bacillus cereus were not detected in any of the samples. Among them， Clostridium perfringens was 3.5×10⁵ CFU/g in the breakfast meat froth food， which was analyzed by whole genome sequencing to compare the molecular typing of Clostridium perfringens originating from the breakfast meat froth food and the anal swabs， which was ST139 type， and the strains all carried cpe virulence gene.Conclusion Through on-site investigation and traceability analysis， it was determined that Clostridium perfringens-contaminated breakfast meat froth was the cause of the foodborne illness outbreak， and that the new technology of whole genome sequencing could play an accurate traceability role in the foodborne illness outbreak.