Ethanol and water are used respectively to extract the active ingredients of eucalyptus leaves. Then it was researched on the inhibitory effect of the active ingredients on MRSA, and compared the inhibitory effect of the oxacillin with and without eucalyptus extracts addition. The results shows that, the ethanol extract of eucalyptus presents a minimum inhibitory concentration(MIC)from 1 g/L to 5 g/L for MRSA, and the water extract is from 2~10 g/L. With 0.2 g/L of ethanol extract of eucalyptus added, the oxacillin can reduce the MIC of the MRSA from 62.5～250 mg/L to 7.8～31.3 mg/L, and the MIC for all kinds of MRSA reduce to 7.8 mg/L except MRSA NO.16 which is reduced from 250 mg/L to 62.5 mg/L after adding in 0.1% water extract. The fractional inhibitory concentration (FIC) index method is used to present that the eucalyptus extract and oxacillin have good synergic inhibitory effect against MRSA, and latex agglutination is used to find that, ethanol extract of eucalyptus inhibit the produce of PBP2’ of MRSA and reduce the drug resistance of MRSA on oxacillin.