An effective method was developed for determination of cadmium in protein powder by microwave digestion-GFAAS with matrix modifier.The effects of NH4H2PO4 mass concentration in tested sample,ashing temperature and atomizing temperature on absorption was discussed.The optimal determination conditions were found by response surface methodology as follows: NH4H2PO4 mass concentration 3.51 mg/mL;ashing temperature 564℃;and atomizing temperature 1 893℃.Under the above conditions,the content of cadmium in protein powder was 0.238 μg/g,the precision relative standard deviation was 2.77%,the detection limit was 0.21 ng/mL,and the average recovery of cadmium in protein powder was 99.5% with a relative standard deviation of 2.82%.