Abstract: OBJECTIVE To establish a RP-HPLC method to determine the contents of protocatechuic acid, protocatechuic aldehyde and tyrosol in Syringa oblate. METHODS The samples were determined by RP-HPLC on a YWG C18 column(4.6 mm×250 mm，10 μm), using methanol-0.125% glacial acetic acid solution(10∶90)as the mobile phase with flow rate of 1 mL·min-1and detected by UV at 275 nm. RESULTS The regression equation of protocatechuic acid: Y=83 995 X－10 368, r=0.999 5，the linear ranges was at 0.08－0.56 μg. The regression equation of protocatechuic aldehyde: Y=111 202 X－35 323, r=0.999 8, the linear ranges was at 0.01－0.07 μg. The regression equation of tyrosol: Y=139 922 X－32 003, r=0.999 6, the linear ranges was at 0.42～2.94 μg. The samples collected in October had the highest contents of protocatechuic acid, while the highest content of protocatechuic aldehyde and tyrosol was in April. CONCLUSION The method is simple，rapid and accurate, and can determine the three components at one time. It can be used for quality evaluation of Syringa oblate. The results show that the optimum collection time of Syringa oblate can be in October or April to May.