Objective:To separate pathogenic bacteria quickly and retrospect the source of food-borne illness.Methods: Remaining food,vomits and feces of those food poisoning patients were detected according to etiology characteristics,meanwhile,antibody detection of double serum in patients was done.Results: Bacillus cereus was detected respectively from cold noodle and vomits,with bacteria count 106 cfu/g,and Bacillus cereus was also found in 2 feces samples.Bacillus cereus antibody from patients′ serum increased more than 4 times.Conclusion: According to Diagnosis Standard WS/T.82-1996,this case of food poisoning was caused by cold noodle contaminated with Bacillus cereus.