Abstract: A series of highly fractionated Ⅰ-type granites, mainly composed of marginal facies fine-grained monzogranite and central facies fine-medium-grained monzogranite, is developed in Linhai forest farm area of the Xiaoxinganling-Zhangguangcailing mountains. The granites are characterized by high Si and total alkali (Na₂O+K₂O), rich Al, and poor Fe, Mg, Ca and Ti, belonging to quasi-aluminous, high-K calc-alkaline series, with enriched LILEs and LREEs, depleted HFSEs, and moderately strong negative Eu anomaly. The LA-ICP-MS zircon U-Pb age results show that the granites were formed at 191.6±2.9 Ma. According to the geochemical compositions, it is considered that the granites are mainly derived from the partial melting of shallow continental crust materials in Early Mesozoic. The discovery of highly fractionated Ⅰ-type granites indicates that large-scale magmatic intrusion occurred in the Early Jurassic, which may be closely related to the regional extensional environment under the westward subduction of paleo-Pacific plate.