The present paper established the determination method of heavy metals such as As, Pb, Hg and Cd in cereals by inductively coupled plasma mass spectrometry (ICP-MS) with microwave digestion. The pretreatment conditions were improved and the instrument operating parameters were optimized. 72Ge, 115In and 209Bi were selected as the internal standard elements to overcome the matrix effects and instrument fluctuations effectively. Interference correction equations were used to eliminate the interference of polyatomic ions. Satisfactory linearity of standard curves was obtained with elemental correlation coefficients over 0.999 9. The detection limits were in the range of 0.000 6～0.016 mg·L-1, the recoveries of samples were 90%～110%, and the RSD was within 5%. The accuracy of the method was evaluated with national standard reference materials and the interference test was experimented using standard solution. Studies have shown that the method is suitable for rapid determination of heavy metals As, Pb, Hg and Cd in cereals with wide linear range, good precision and high accuracy.