The Baiyinnuoer Pb-Zn deposit in Inner Mongolia is the largest one in Greater Hinggan Mountains. The ore-bodies in the deposit mainly occur along the contact zone of the granodiorite (or granodiorite porphyry)and marble. In order to determine the source of the ore-forming materials, the sulfides from the ores, and whole rocks from strata and intrusive rocks in Baiyinnuoer Pb-Zn deposit were analyzed for the Pb isotopic compositions. The results showed that N (206Pb)/N(204Pb) of the sulfides from the ores ranged from 18.266 to 18.372 with an average of 18.296, N(207Pb)/N(204Pb) ranged from 15.501 to 15.579 with an average of 15.536, and N(208Pb)/N(204Pb) ranged from 38.016 to 38.339 with an average of 38.138.