To establish the method for qualitative and quantitative determination of gallic acid in Herba Gei. Gallic acid content is determined by HPLC with Diamonsil C18 column as the stationary phase, under the conditions of methanol-0.1% phosphoric acid in water (10:90) mobile phase, 271 nm detection wavelength, and 40? column temperature. Peak area of gallic acid shows a good linearity with the injection volume within a 0.202~1.212 μg range, r=0.9997; average recovery is 99.26%, RSD 2.20%. Through quantitative determination of Herba Gei of different origins, the method established herein is confirmed to be simple, fast, sensitive, accurate, reliable and reproducible.