There exists a NW-SE trending Indosinian granitoide belt in the Qinghai Nanshan tectonic zone, The genesis study on this granite zone has great scientific significance for investigating the transitional relation between the west Qinling and the Qilian orogenic belts in Paleozoic Tethys evolution stage．As a granitic complex in the west section of the belt，the Dangjiasi granitic complex dominantly consists of granodiorite pluton and monzogranite pluton．In this paper，a detailed study for the LA-ICP-MS zircon U-Pb dating，petrology and geochemistry characteristics was made for the Dangjiasi granitic complex．The results show that the crystallization ages of the Dangjiasi granodiorite and monzogranite are 240.1±2.1Ma and 241.0±2.6Ma，respectively，belonging to the Middle Triassic．The whole rock geochemical data show that the Dangjiasi granitic complex is relatively rich in SiO2（66.37%~73.99%)and K2O (3.37%~4.73%）．The granitic rocks are metaluminous to weak peraluminous，and belong to high-K calc-alkaline I-type granite．The rocks are rich in LREE and depleted in HREE．The REE patterns show rightward incline and moderate negative Eu anomaly（δEu=0.32~0.64）．The trace element geochemistry is evidently characterized by positive anomaly of LILE（e.g. Cs，Rb，K）and negative anomaly of HFSE（e.g. Nb，Ta，P，Ti）．Dangjiasi grantic complex were mainly originated from the partial melting of lower crustal basic rocks，with minor mantle-derived component．According to analyses of regional geological setting，we suggest that Dangjiasi granitic complex were formed in the stage of the southward subduction of Zongwulong Oceanic crust．