Abstract: The concentration of Cd, Pb in herb sample was determined by isotope dilution ICP-MS. The sample was digested by high-pressure vessel with HNO3/H2O2 as the solvent. By measuring the ratio of 112Cd/111Cd, 208Pb/207Pb and the spike addition, the Cd, Pb concentration can be determined, and the uncertainty of the measurement results was also analyzed and evaluated. Furthermore，this method was used in CCQM-P97 (Cadmium and Lead in Herb) and good agreement was achieved, which indicated the validation of this method.