Abstract: The study on the petrology, geochemistry, genesis and tectonic environment of the granite porphyry in Tegewula area of Daxinganling Mountains show that the age of the rock is 145.9±1.2 Ma, formed in the late Early Cretaceous. The granite porphyry is rich in silicon, alkali and aluminum, belonging to the quasi aluminous-aluminous high-potassium calc-alkaline series. The mineral assemblage and geochemical characteristics show that the granite porphyry is highly differentiated I-type granite, with enriched LILEs (Rb, Th and U) and LREEs (La, Ce and Pr), and obvious negative Eu anomaly, indicating the geochemical characteristics of crust-derived magma or magma mixed with crustal materials. It is concluded that the granite porphyry in Tegewula area was formed in a post-orogenic extensional environment, which may be related to the delamination of thickened continental crust after the closure of Mongolia-Okhotsk suture zone.