To establish a sensitive and good reproducibility method of determining aristolochic acid A in Yishen Juanbi pill.RP-HPLC method was adopted.Diamonsil C18 column, 5μm, 4.6×250 mm was used.The mobile phase was methanol-water-acetic acid (69:30:1) at a flow rate of 1.0 mL/min, and the column temperature was 35°C.The UV-detection wavelength was 250 nm.The results suggested that under the range from 0.011 to 0.304μg and the regression equation Y=5308818X-4676, the recoveries (n=9) of the method was 99.31%.The method was accurate, sensitive, specific, and suitable.