To study the effects of Fuzheng Jiedu Huayu Decoction on the expression of MexAB-OprM efflux pumps in multidrug-resistant Pseudomonas aeruginosa.Methods:The minimum inhibitory concentration of piperacillin-tazobactam and the minimum bactericidal concentration of the water extract of Fuzheng Jiedu Huayu Decoction were determined via microdilution method for selected MexAB-OprM positive Pseudomonas aeruginosa strains so as to determine the concentration of piperacillin-tazobactam and the water extract of Fuzheng Jiedu Huayu Decoction in the culture medium during the fluorescence quantitative PCR of bacterial samples.The bacterial growth curve was drawn and the culture time of the bacterial samples was determined.The expression levels of mexB，oprM，and mexR before and after drug intervention were detected by real-time fluorescence quantitative PCR technology.Results:The expression levels of mexB and oprM in MexB-OprM efflux pump positive strains were decreased after the intervention of Fuzheng Jiedu Huayu Decoction water extract(P<0.05)，and that of mexR was increased than before(P<0.05).Conclusion:The therapeutic effect of Fuzheng Jiedu Huayu Decoction on pneumonia caused by MDRPA may be attributed to the inhibition of the expression of MexAB-OprM efflux pump.