Abstract: Objective To identify an outbreak of food borne salmonellosis and trace its molecular source. Methods The outbreak strain of Salmonella from food in Huangpu district Shanghai in year 2007 was collected.It was tested with three kinds of Salmonella reference sera by contrast test of serological identification.This strain was tested for antibiotic resistance and multiple locus sequence analysis test (MLST) .Using non-typhoidal Salmonella of China Pulse Net data bank, the pulsed field gel electrophoresis (PFGE) of outbreak strains between Shanghai and Chongqing were compared with cluster analysis. Results The strain of Salmonella from food-borne outbreak in a construction site of Shanghai Huangpu district was identified as Salmonella enterica subsp.enterica serovar Thompson (S.Thompson) ST26 by serological test and MLST.The outbreak strains were 100% resistant for six antibiotics (Tetracycline, Amoxicillin/clavulanic aci, Ampicillin, Chloramphenicol, Nalidixic acid and Sulphofurazole) .Another outbreak strain belong to Salmonella serogroup C from food-borne cases in Chongqing year 2007 were also identified as S.Thompson ST26 by rechecking.They were homologous in genetics with the outbreak strains of S.Thompson in Shanghai. Conclusion There are cross agglutination factor of C and K in H-phase between the antisera from Lanzhou biologicals Institute and the antisera from S&A Thailand.The outbreak strains of Salmonella from food-borne in Shanghai Huangpu district in year 2007 may be intreduced by the transferred clone of S.Thompson ST26 with multiple drug resistance.