Through nearly ten years of geological exploration, several ore deposits with high economic values in the northern Gangdese have been developed and utilized; therefore, this belt has become another hot spot of geological exploration and research in Tibet. The Chengba deposit is the only medium- large sized Cu- rich deposit newly discovered in the northern Gangdese belt. It is typical of a skarn depositswhich consists mainly of garnets. Cu- bearing orebodies at the Chengba deposit occur in interlayers between the Linbuzong Formation hornfels and Duodigou Formation marble as strata or veins, accompanied with secondary Mo, Zn, Au, Ag and Bi. On the basis of the geological background and geological characteristic of ore deposit, Re- Os dating of molybdenite yields a model age of 58. 2～58. 8Ma and an isochron age of 58. 49±0. 43Ma（MSWD=0. 61）, determining that the Chengba Cu deposit is the product of mineralization in the main collision stage. The discovery of the Chengga copper deposit confirms that copper deposits can be formed from main collisional process of the Gangdese metallgoenic belt. Therefore, the composite model of the deposits in the main collision stage should be modified into the skarn Cu(Mo)+skarn Fe- Pb- Zn- Mo(Cu)+porphyry Mo(W) from the previous study ones. In addition, Re contents of molybdenite range between 84. 6×10-6 and 461. 3×10-6 (ave. 252×10-6), indicating that the ore- forming materials of the Chengba Cu deposit are characterized by mixing of the crust and mantle.