Abstract: Objective To induce multidrug resistance of the sensitive strain of Shigella flexneri and to study the multidrug resistance regulating gene mutations.Methods Clinical sensitive Shigella flexneri strain was induced into anti-drug strain by 1/2 minimum inhibitive concentration(MIC) induced trails of four antibiotics.MarOR gene in sensitive and induced anti-multidrug strain was amplified with polymerase chain reaction(PCR).The PCR products were sequenced and compared.Results Induced anti-multidrug strain of Shigella flexneri was obtained successfully.The strain was resistant to gentamycin(GF),norfloxacin(NOR),cotrimoxazole(SMZ),and cefalotin(CF).DNA sequence analyses of marOR in sensitive and induced anti-multidrug strain revealed seven point mutations.Conclusion The marOR gene mutations may play an important role in the regulation of multi-drug resistance in Shigella spp.