There exist three stages of magmatic emplacement in the Banbanshan complex massif, Shanyang County, on the northern margin of the South Qinling Mountains. They are the early monzogranite, the middle K-feldspar granite and the late diabase. In this paper, the authors studied the geochemistry and LA-ICP-MS zircon U-Pb age of the early monzogranite. The results show that the SiO₂ content of monzogranite is between 73.35% and 77.49%, the content of total alkali (K₂O+Na₂O) is 3.15%~7.19%, the Rittman index is 0.30~1.66, and the A/CNK ratio is 1.18~2.48, suggesting that they belong to peraluminous S type granite with medium and high potassium calc-alkaline nature. The total amount of rare earth elements varies greatly. Light rare earth elements are relatively enriched and heavy rare earth elements are relatively deficient. The rocks have a weak negative europium anomaly (δEu=0.70~0.89). Large ion lithophile elements Rb, K, Th, Ba are relatively enriched, and high field strength elements Nb, Ta, Ti, P are relatively deficient. It is shown that the Banbanshan monzogranite was formed in the same collisional tectonic environment and carried the geochemical characteristics of the volcanic arc environment, suggesting that the magma originated from the partial melting of the upper crust rocks and was metasomatized by the residual fluid formed by the dehydration of the subducted oceanic crust. The zircon U-Pb ages of the two samples are 743.2±6.1 Ma and 743.7±5.9 Ma, respectively, indicating that the Banbanshan monzogranite was formed in Neoproterozoic. Combined with the previous research results, it is considered that the Banbanshan area had been in the stage of paleooceanic subduction before 743 Ma, and after 743 Ma, the paleooceanic basin was closed, Rodinia supercontinent began to converge, and land collision occurred.