The Luotuobozi pluton, located in the southeast of Haduohe area Great Xing’an Range, with its geotectonical position in the east of Xing’an-Mongolian Orogenic belt, is composed of syenogranite, granodiorite(with dioritic enclaves), monzonite. Such characteristics of zircons from sample imply their magmatic origin, as euhedral shape, typical oscillatory zoning and high Th/U ratios. LA-ICP-MS zircon U-Pb dating indicates that the ages of zircons from Luotuobozi pluton are syenogranite: 127±1Ma, granodiorite: 126±1Ma, dioritic enclaves: 131±1Ma, monzonite: 130±1Ma, concentrated in Early Cretaceous. The rock is weak peraluminous belonging to high potassium calc-alkaline series, characterized by high Si (SiO2=71.11%~76.89%), high Alkali (Na2O+K2O=8.04%~9.17%), high aluminum (Al2O3=12.9%~14.99%) and low titanium (TiO2=0.08%~0.22%), with A/CNK value 0.97~1.10. The rock experiences a highly fractionated and evolving stage reflected from DI (86.1~97.46) and SI (0.1~5.59), with negative and positive Eu anomalies (δEu=0.26~2.51) reveals LREE enrichment (LREE/HREE=6.35~32.16) and HREE depletion (LaN/YbN =6.35~32.16). The rock are also rich in Th, U, Hf, Zr, La, Rb and depleted in Ti, Ta, Nb. TFeO/MgO ratios are relatively low (=2.37~6.41), Zr+Nb+Ce+Y=106.48×10-6~162.74×10-6, they are less than that of the low-limit values of the A-type granites. Zircon saturation temperatures of them range from 723.43 to 760.48℃ which are also less than that of the low-limit values of the A-type granites. Combining petrography, rock geochemical characteristics, chronology, and regional geological feature, the Luotuobozi pluton belongs to highly fractionated high-potassium calc-alkaline I-type granites, the formation of this pluton is probably by the extensional continental lithosphere thinning in northeast China after the subduction of the Pacific plate in Mesozoic.