Triterpene acids components in leaves of Rosmarinus officinalis Linn. were separated and identified by HPLC， silica gel column chromatography and reversedphase C₁₈ semi-preparative liquid chromatography method. And taking the minimum inhibitory concentration （MIC） as the index， the inhibitory activity of each compound was determined. The results show that 4 triterpene acids compounds are isolated from ethanol extracts of leaves of R. officinalis； according to the peak characteristics of reference substances， compound 2， 3 and 4 are identified as betulinic acid， oleanolic acid and ursolic acid， respectively； based on physicochemical constants and spectral data， compound 1 is identified as Δ^20（30）-ene-ursolic acid. Ursolic acid， Δ^20（30）-ene-ursolic acid and oleanolic acid have a certain inhibitory activity to Gram-positive strains （methicillin-resistant Staphylococcus aureus， MRSA）， in which， the MIC value of ursolic acid to MRSA is 8.000-128.000 μg·mL^-1， and its inhibitory activity is the strongest； however， none of 4 compounds shows inhibitory activity to Gramnegative strain （Escherichia coli S002）.