[Objective] To develop an HPLC method for the simultaneous determination of free and hydrolyzed protocatechuic acid and gallic acid in Geranium sibiricum.[Method] Agilent SBC18 column(4.6 mm ×250.0 mm,5 μm),mobile phase of acetonitrile-0.2% H3PO4(4:96),the flow rate of 0.8 ml/min,the detection wavelength of 253 nm and the room temperature as column temperature.[Result] The average recoveries of free protocatechuic acid and gallic acid were 98.42% and 97.36% respectively with RSD of 1.47% and 1.56%;while the average recoveries of hydrolyzed protocatechuic acid and gallic acid were 99.58% and 99.43% with RSD of 1.79% and 1.44%.The average contents of free protocatechuic acid and gallic acid in the samples were 0.001 2% and 0.041% respectively;the average contents of hydrolyzed protocatechuic acid and gallic acid were 0.013% and 1.387% respectively.The linear relationships of protocatechuic acid and gallic acid were in the range of 0.204-1.02 μg(r=0.999 3) and 0.078-0.39 μg(r=0.999 4) respectively.[Conclusion] The method described in this paper was simple and accurate with good reproducibility,which could be adopted for the quality control of Geranium sibiricum. [Objective] To develop an HPLC method for the simultaneous determination of free and hydrolyzed protocatechuic acid and gallic acid in Geranium sibiricum. [Method] Agilent SBC18 column (4.6 mm × 250.0 mm, 5 μm), mobile phase of acetonitrile-0.2% H3PO4 (4:96), the flow rate of 0.8 ml / min, the detection wavelength of 253 nm and the room temperature as column temperature. [Result] The average recoveries of free protocatechuic acid and gallic acid were 98.42% and 97.36% respectively with RSD of 1.47% and 1.56%; while the average recoveries of hydrolyzed protocatechuic acid and gallic acid were 99.58% and 99.43% with RSD of 1.79% and 1.44%. The average contents of free protocatechuic acid and gallic acid in the samples were 0.001 2 % and 0.041% respectively; the average contents of hydrolyzed protocatechuic acid and gallic acid were 0.013% and 1.387% respectively.The linear relationships of protocatechuic acid and gallic acid were in the range of 0.204-1.02 μg (r = 0.999 3) and 0.078 -0.39 μg (r = 0.999 4) respectively. [Conclusion] The method described in this paper was simple and accurate with good reproducibility, which could be adopted for the quality control of Geranium sibiricum.