Abstract: The contents of two levels of lead in Sn-Ag-Cu system solder for CCQM comparisons were determined by isotope dilution mass spectrometry (IDMS) after the samples were mixed with ²⁰⁷Pb spike and digested by H₂O₂-HF in PTFE vessel. H₂O₂-HF digestion system avoided forming silver chloride and β-stannic acid when using conventional nitric acid and hydrochloric acid for Sn-Ag-Cu solder, and saved the digestion time. Matrix effects on ²⁰⁸Pb/²⁰⁷Pb ratio determination and the resulting Pb contents in solder were discussed, and the result shows matrix effect was reduced by selecting the appropriate dilution factor in the case of guaranteed precision. Established accurate determination method for high and low level of lead in Sn-Ag-Cu system solder, the uncertainty of the measurement was also analyzed and evaluated. The good degree of equivalence of CCQM-P119 and CCQM-K88 indicates IDMS has good accuracy and small uncertainty compared with traditional methods, it validate reliability of this method. The established IDMS method is suitable for the certification of similar solder reference materials.