A new pretreatment method for the determination of cadmium in grain was developed: citric acid extraction method. The basic parameters affecting the citric acid extraction were optimized, and the best pretreatment conditions were obtained. The accuracy of the method was investigated by using certified reference materials and reference materials. The citric acid was fixed in 10 mL centrifuge tube, which provided technical support for the application of this method. After optimization, only citric acid and water are needed to determinate the cadmium in grains. The detected results of certified reference materials and reference materials were all within the assigned values. The RSD of 7 independent tests was less than 5%. The method has good precision and accuracy. The detection limit and quantitative limit of the method are 0.039 ng/mL and 0.129 ng/mL, respectively which can meet the requirements of cadmium detection in grains. The whole pretreatment process can complete in 15 minutes, which is safe, green, simple and easy to operate.