Objectives:As a granitic pluton in the west part of the Qinghai’nanshan tectonic belt，the Heimahe granitic pluton are mainly composed of granodiorite, quartz diorite, diorite and gabbro. The formation age and geochemical affinity of those rocks play a key role for investigating the transitional relation between the west Qinling and the Qilian orogenic belts in Paleozoic Tethys evolution stage． Methods:In this paper，a detailed study of LA-ICP-MS zircon U-Pb dating，petrology and geochemistry characteristics was carried out for quartz diorite，granodiorite and mafic microgranular enclaves from the Heimahe granitic pluton． Results:The LA-ICP-MS zircon U-Pb ages of the granodiorite and MMEs are 244.4 ± 1.1 Ma and 243.0 ± 1.2 Ma，respectively，indicating that the Heimahe granitic pluton formed in early Middle Triassic．The whole rock geochemical data show that quartz diorite and granodiorite belong to the metaluminous high-K calc-alkaline series and MMEs are high-K calc-alkaline to alkaline series．The REE patterns display rightward incline and weak negative Eu anomalies（δEu = 0.65 ~ 0.83）．The trace element geochemistry is evidently characterized by positive anomaly of LILEs（e.g. Cs，Rb，Th，K）and Pb，negative anomaly of HFSE（e.g. Nb，Ta，Ti）and P，Ba． Conclusions:The petrographic and geochemical characteristics of the Heimahe granitic pluton imply a closely subductionrelated origin at active continental margin arcs，with crust—mantle mixing characteristics．The mafic magma was derived from partial melting of the mantle wedge which was metasomatized by hydrous fluids from subduction slab dehydration. Then the quartz diorite originated from crystallization differentiation of mantle source magma，and the granodiorite originated from crust sourced magma mixing some mantle sourced magma．Connecting with the predecessors research results，it can be supposed that the petrogenesis of the Heimahe granitic pluton may be related to the southward subduction of Zongwulong Oceanic crust during the early Middle Triassic．