Scme certified reference materials (CRMs) were digested and the elemental concentrations were determined by ICP-MS instrument, and the results include not only the trace key elements such as As, Pb, Hg and Cd but also the major components such as Ca, Fe, K, Na etc. The digestion method, the recoveries, and the detection limits are discussed to piove the reliability of ICP-MS and EPA200.8 method for the determination of the elements in fcxxl and plant samples. The ICP-MS instrument with ORS (octupole reaction system) was applied to the determination of As, Se etc, and the results are compared with those from the normal ICP-MS without ORS. The removal of ArCl and ArAr interference is discussed, and the advantage of ORS is proved by measuring the As and Se in some CRMs.