Rice were grounded into rice powder by muller and soaked in mixed acid solution (concentrated nitric acid:concentrated sulphuric acid=3∶2) for 12 hours. Then, the mixture was heated slowly in a hood, and mixed acid solution and aqueous hydrogen peroxide solution were added for the digestion. In order to test the trace amount cadmium in rice with square wave stripping voltammetry method, a three-electrode system are used with the silver-based mercury film electrode as working electrode, platinum electrode as counter electrode, and saturated calomel electrode as reference electrode. The results show that a good linear relationship can be obtained in pH=3.0 NH4Cl（0.2 mol/L）substrate solution, within the concentration of cadmium 0.01~ 0.12 μg/mL; the regression equation was Ip=497.59c+15.324 with the correlation coefficient of 0.994 1, the detection limit of 4.607 4×10-3 μg/mL, the relative standard deviation of 4.12%~5.56%, and the recovery rate of 90.26%~98.16%.