AstudyofPt-metabolitesfromanewanti-hepatomadrugmiriplatinwasimportanttomiriplatin's pharmacology research. Therefore, a method based on size exclusion chromatography-inductively coupled plasma mass spectrometry ( SEC-ICP-MS) was developed to study miriplatin and its Pt-metabolites in Beagle dog plasma. This method could be used to study total platinum concentration half-quantitatively. Compared with traditional ICP-MS direct determination, data acquired from this SEC-ICP-MS method were almost the same. By using BioSep-s2000 column, 25 mmol/L of pH 7. 2 phosphate buffer as eluent, and Pt-195 as detecting isotope, we discovered miriplatin with its four Pt-metabolites in dog plasma after intra-hepatic artery administration. The main Pt-metabolite was m2 , which associated with plasma proteins. Miriplatin in plasma did not bind with plasma proteins. According to calculation, the ratio of miriplatin/m2 first decreased rapidly, and then slowly increased to its second climax, finally slowly decreased.