Ara?uaí-West Congo orogenic belt is the product of the Neoproterozoic Brasilia-Pan African movement. It belongs to the northern branch of the Adamastor Ocean and has developed a complete Wilson cycle. The Aracuai Belt has been studied to a relatively high degree, with the development of granitic mantle related to Neoproterozoic-Cambrian subduction and collision. However, magmatic rocks of this period in West Congo Belt have rarely been reported, and even their existence has been questioned. Whether there are granites related to Neoproterozoic -Cambrian subduction and collision in the West Congo Belt is worth further study. In order to reveal the Ediacaran tectonic transition process of West Congo orogenic Belt, this paper studies the petrology, zircon U-Pb chronology and geochemistry of the newly discovered quartz diorite and quartz diorite in the northwest of Angola, analyzes the genesis of the rocks and the tectonic environment in which they formed. The zircon U-Pb ages of quartz diorite and quartz diorite were 578.0±2.3Ma and 543.9±2.6 Ma respectively, belonging to the middle and late intrusions of the Ediacaran period of the Neoproterozoic. Quartz diorite is rich in hornblende, biotite and plagioclase, belonging to the quasi-aluminous potassium-calc-alkaline series. It has the characteristics of island arc magmatic rocks, enriched with large ion lithophile elements such as Ba and K, deficient in Th, U, Ta, Nb, P, Ti and other high field strength elements, and the rare earth partition curve is right-leaning type of LREE enrichment. It is the product of crust-mantle mixing under subduction mechanism, which can be compared with the G1 suite in Ara?uaí belt. Quartz monzodiorite is rich in biotite and plagioclase and belongs to high potassium calc alkaline peraluminous rock. Compared with quartz diorite, it is rich in K2O, Na2O, Al2O3, P2O5 and poor in CaO, MgO, Fe2O3T. Quartz monzoniorite is the product of partial melting of the mafic lower crust under the post-collision background, which can be likened to the G3 suite in Ara?uaí belt. Studies show that there exists a Neoproterozoic calcium-alkaline magmatic arc related to orogeny in West Congo Belt. The two periods of magmatic rock ages (578 Ma vs. 544 Ma), geochemical characteristics and tectonic backgrounds are significantly different, indicating that the West Congo orogenic belt underwent a tectonic background transformation from subduction to post-collision from the middle to the end of the Ediacaran period.