Cretaceous magmas are widely distributed within and on both sides of the Bangonghu-Nujiang suture zone. These magmatic rocks record the process of the subduction of the Bangonghu-Nujiang ocean and the collision between the Lhasa and Qiangtang terranes. In this study, we report new zircon U-Pb dating, petrogeochemistry, and zircon Hf isotopic analysis of biotite monzogranites from the Naqu area in the middle of the Bangong-Nujiang suture zone. Zircon LA-ICP-MS dating results show that biotite monzogranites were formed at the Early Cretaceous (114～113 Ma). All samples have high-K calc-alkaline or potassic basaltic affinities. They also show high Ga/Al×10000 ratios (in the range of 2.02～3.15, with an average of 2.61) and Zr+Nb+Ce+Y contents (with an average of 524.87×10^-6, much higher than 350×10^-6) with high zirconium saturation temperature and Ti-in-zircon thermometer (>800℃). These features suggest that these samples belong to the A-type granites. The zircons in the granites have low ε Hf( t ) values (10.1～6.4) and ancient two-stage Hf model ages ( t DM2) (1852～1547 Ma), indicating that the magma was originated from anatexis of the middle-lower crustal crystallization basement of the Amdo microcontinent. Combined with previous works, we suggest that the Naqu biotite monzogranites may have been formed in post-collisional setting. At the late Early Cretaceous, the Bangong-Nujiang Meso-Tethyan ocean have been closed by the Lhasa and Southern Qiangtang collision.