Yili porphyry Mo deposit, located in Oroqen of Inner Mongolia, is a newly discovered medium-scale ore deposit in recent years in the northern Great Khing’an Ranges. The host rocks are Late Paleozoic granites and Woduhe River Formation. Late granitic porphyry dikes have been found in deep by drilling. The metallogenic model of Yili Mo deposit is similar to the ‘body within body’ model. The granites emplaced in late stage are characterized by high SiO2, alkalis comprises K2O and Na2O, Al2O3, and low MgO, TFeO, CaO. The K2O/Na2O=0.76~1.27, A/CNK=1.02~1.23. With respect to trace elements of these granites, enrichment of Rb, U, K, Pb, relative depletion of Nb, Ta, Ti, P and LREE, (La/Yb)N=11.09~22.41, depletion of HREE and slightly negative Eu anomalies (δEu = 0.63-0.92) are the major characteristics. These granites show geochemical affinity of adakite also with low Ni, Cr content and Mg#, high Sr/Y. This study carried out the LA-MC-ICP-MS U-Pb isotopic dating for zircons from late granites (biotite granites and granitic porphyry) and molybdenite Re-Os isotopic dating from ore body and obtained their corresponding age data are 132.43±0.61~134.46±0.58 Ma and 131.8±1.5 Ma, respectively, are belongs to early Cretaceous. The rock-forming age is earlier than the ore-forming age 2.7 ~ 0.6 Ma. Combined with results of melting experiment and regional data, these granites were produced by partial melting of thickened lower crust, while trigger mechanism of Mo mineralization is the delamination of thickened lower crust after melting. A concealed granitic intrusion, is directly related to mineralization, may emplaced in deep of mine. Statistics precise chronology data of molybdenites and granitic rock-forming indicate that there occurred 4 periods of Mo-mineralization during Phanerozoic in Northern Great Khing’an Ranges. These periods of Mo-mineralization are early Caledonian (510~470Ma), late Variscan (300~290Ma), late Indosinian-early Yanshanian (205~175Ma), early stage of middle Yanshanian (late Jurassic, 150~145Ma) and late stages of middle Yanshanian (early Cretaceous, 143~129Ma). The Mo mineralization of late Indosinian-early Yanshanian and middle Yanshanian are the major metallogenitic periods. Yili Mo deposit is one of the products of late stages of middle Yanshanian Mo-mineralization in the peak of metallogenitic period in the northern Great Khing’an Ranges.