Abstract: A method for determination of genistein by quantitative nuclear magnetic resonance (qNMR) was proposed, using vanilmandelic acid as the internal standard. The measurement conditions with inverse gated decoupling technology were as follows:the relaxation delay time was 40 s, the number for scanning was 32, the acquisition time was 4.0 s, and the solvent was deuterated dimethyl sulfoxide. The peak of δ 6.38 in genistein was selected as the quantitative peak, and peak of δ 6.96 in vanilmandelic acid was selected as the internal standard signal peak. As shown by the results, linear relationship between the peak area ratio of quantitative peak to internal standard signal peak and mass ratio of genistein to vanillic acid was found in the range of 0.83-7.50, with detection limit (3.3s/k) of 0.2 g·L^-1. And RSDs of the determined values (n=6) was less than 0.35% in the precision test. The stability test showed that the test solution was stable for 24 h in the dark. This method was applied to the analysis of actual samples, and the determination result was consistent with that of the national standard GB/T 23788-2009.