Geza island arc belt is one of the important tectonic units in the archipelagic arc-basin system in the Sanjiang area (Jiasha River, Nujiang River, Lancang River), which is located in the eastern edge of the Dege-Zhongdian continental blocks Ganze-Litang and the southern of Yidun ia land arc. It began at Ganze-Litang oceanic crust westward subduction in the Late Triassic, experienced intracontinental convergence and post-orogenic extensional phase in Yanshanian, and shows a strong thrust-nappe structure and large-scale strike-slip translation activities by the effect of the collision uplift of the Qinghai-Tibet Plateau in the Himalayan. In this area, there were strong magmatic activities, superior metallogenic geological conditions, the rich mineralization and a lot of deposits. It was a newly discovered copper polymetallic ore concentration area of China in recent years, in which the porphyry copper deposits in the pulang complex is a typical representative of Indosinian porphyry copper deposits. Through the study of apatite fission track, geochronology of the major mineralized porphyry indicates that fission track age distribution in 12~68Ma and less than the age of diagenesis and mineralization,the denudation rate of the major porphyry mineralization is 0.046～0.236mm/a, denudation is about 1473～2904m. The comparative studies of emplacement depth and denudation degree show that erosion depth of the ore-forming rocks was basically less than emplacement depth,which was more favorable to the preservation of deposit after it formed. According to the quantitative calculation of erosion amount of resources to mainly porphyry deposits, the denudation was divided into three orders of magnitude: Grade I for mild denudation of deposit, GradeⅡ for medium denudation of deposit, Grade Ⅲ for severe denudation of deposit, which provides the theory basises for evaluation of the metallogenic potential and deep prospecting of porphyry metallogenic system.