The Yongqing granodiorite, located in the inner part of the Jiamusi massif in eastern Northeast China, was previously considered as a part of the Early Paleozoic Mashan complex. LA-ICP-MS zircon U-Th-Pb isotopic analysis yields a middle Permian age of 265±1 Ma (MSWD=2.1). The granodiorite is composed of subhedral to euhedral plagioclase (30%～35%), anhedral quartz (25%～30%), anhedral K-feldspar (20%～25%) and subhedral biotite (10%～15%). Geochemically, the granodiorite is high-K calc-alkaline to calc-alkaline and peraluminous in composition, and shows very good linear correlation between Sm/Dy and Dy, Sr/Y and Y, and Ce/Sm and δEu, probably resulting from assimilation and contamination of some country rocks during the emplacement without melt fractionation. Taking the effects of assimilation and contamination into consideration, the authors hold that the high Sr/Y and Sm/Dy ratios of parental magma of the Yongqing granodiorite might imply the presence of garnet in the source. The depth of the source rocks might have been greater than 25 km, distinctly different from the depths of contemporaneous intrusions in southern Jiamusi massif and the Zhangguangcai Mountain. Combined with previous studies, it is suggested that the Yongqing granodiorite was formed during or after the collision between the Jiamusi massif, Songnen block and Xingkai block.