Abstract: Three isoflavones: irigenin, tectorigenin and tectoridin in Belamcandachinensis ( L.) DC. and Iris tectorum Maxim were determined by square wave voltam-metry. At the potential of - 1.34 V (vs Ag/AgCl ) the isoflavones gave well- definedpeaks in the buffer solutions of pH3 ～5. An excellent linear relationship was obtainedbetween the peak current and concentration. The method can be used to analyze smallamounts of sample.