Ore-forming materials of contact metasdmatic skarn type Cu-Pb-Zn polymetallic deposits which occur in the contact zone of igneous rocks and country rocks are considered traditionally as the result of magmatic differentiation. According to the Pb isotopic composition, four types of relationships among ore lead, magmatic rock lead and country rock lead may be distinguished: ( 1 ) ore lead is consistent with magmatic rock lead and very different from country rock lead; ( 2 ) ore lead, ratios are higher than those of magmatic rock lead. and. lower than those of country rock lead; ( 3 )ore lead, ratios are lower than those of magmatic rock lead and higher than those country rock lead; ( 4 ) the 206Pb/204Pb ratio of ore is lower than those of magmatic rock lead and. country rock lead.. Ore lead of type 1 deposits is derived from magma; ore leads of types 2 and 3 deposits are the mixture of magmatic rock lead and country rock lead, and ore lead of type 4 deposits is the mixture of magmatic rock lead, country rock lead and lower crust lead.