Abstract: Caledonian granites in the northern segment of the Zhuguang Mountains were studied by using the unit superunit mapping method. The results indicate that the Guidong sequence and Zuo’an superunit have the characteristics of I type granites and were formed in a pre collision environment and that the Tanghu superunit is represented by S type granites, and originated in a syn collision environment. By integrating all geological and geochemical factors, it is inferred that the geodynamic process of their formation experienced two events of intracontinental detachment and subduction: the first detachment produced the magma of the Guidong sequence, and the second detachment the magma of the Zuo’an superunit; meanwhile, strong compressive stress led to thickening of the crust between two detachments and partial melting of upper mantle material, thus forming the Tanghu superunit.