There are a mass of cretaceous granitoids in South Qiangtang massif of northwestern Tibetan Plateau (north of western Bangonghu-Nujiang suture), Hongqilapu pluton is one of these granitoids, it comprises major granodiorite and minor diorite. Referring to the cathodoluminescence (CL) image and Th, U, REE of zircon, the age of this pluton is 107.2±0.9Ma which belongs to the late of Early Cretaceous by the method of zircon LA-ICPMS U-Pb dating. The geochemistry show that, the pluton leans to intermediate, are high in Al, Ca and K, shows low content of ΣREE, and moderate or weakly negative Eu anomaly, are enriched in LILE(Rb, Th, K, LREE), and poored in HFSE(Nb, Ta, P, Ti, HREE), is high K calc-alkaline I type granite with metaluminous to slightly peraluminous. Partial melting and crystallizatiion-differentiation played an important role in magmatic evolution, and ever taked place the crystallizatiion-differentiation of plagioclase, apatite and titanic magnetite. The features of high CaO, CaO/Na2O ratio, depletion in Nb、Ta, low in Mg#, enriched in K and Sr isotope show that the pluton was fromed by remelting of the amphibole facies basaltic rocks in lower crust. The pressure of the source region was >1.5Gpa (the thickness of crust was 50Km at least) which based on the low in Y, HREE , high in Al2O3、Sr、Sr/Y ratio, the structure of intergrowth beween quartz and alkali feldspar,and the diagrams of SiO2-Mg#, SiO2-Al2O3, the initial temperature of magma was >788℃ which based on the saturation temperatures, structure, and U-Pb isotopes of zircon, these conditions of warm-pressing was in accordance with the formation of the granite with high Sr and low Yb(adakite), and the remain should be garnet+amphibole+rutile(without plagioclase). Based on the regional geological information, the pluton should be the product of thickening crust which was caused by the collision beteew Gangdese massif and Qiangtang massif with the closing of Bangonghu-Nujiang ocean, it illustrates that the time of western and mideastern Bangonghu-Nujiang ocean should be the same.