Abstract: A method for determination of oleanolic acid in quinoa by high performance liquid chromatography (HPLC) was established. Quinoa sample of 1.5 g was dissolved in 40 mL of methanol and 10 mL of 3 mol·L^-1 hydrochloric acid solution, and oleanolic acid was extracted by ultrasonic for 20 min, following by reflux hydrolysis for 1.5 h, which could convert oleanolic acid into aglycone in order to avoid the interference of impurities. A mixture of methanol and 0.1 mol·L^-1 ammonium acetate solution at volume ratio of 85:15 was used as the mobile phase, and the content of oleanolic acid in the sample extract was determined by HPLC. As shown by the results, linear relationship between mass concentration of oleanolic acid and its peak area was kept in the range of 5-500 mg·L^-1, with detection limit (3S/N) of 0.3 mg·kg^-1. Recovery test was made on quinoa samples at 3 concentration levels by standard addition method, giving results in the range of 98.0%-101%, and RSDs (n=5) of the determined values ranged from 4.2% to 7.5%. This method was applied for determination of oleanolic acid in 12 actual samples, and the detection amounts of oleanolic acid were in the range of 0.51-21.26 g·kg^-1.