The Yidun arc collision-orogenic belt is a composue orogenic belt of the giant Tethys-Himalaya orogenic zone. Based on 43 isotopic ages of 29 granite bodies in combination of their petro-geochemistries, the paper established a time coordinate for the granites of the orogenic belt. Four genetic types of the granites were identified as follows: Indosinian arc granites, early Yanshanian syn-collision granites, late Yanshanian A-type granites and Himalayan intra-continental granites. The formation and evolution were reconstructed. A large-scale Indosinian subduction-orogenesis led to the formation of the Yidun magmatic arc (238-210 Ma). From about 206 Ma there occurred arc-continent collision accompanied by compressional contraction and shearing deformation of the arc crust and development of syn-collision granites. In the late Yanshanian epoch (138-73 Ma) post-orogenic extension came into action and resulted in the generation of A-type granites. During the Himalayan (65-15 Ma) intra-continental orogenic movement a large-scale strike-slip thrusting induced the intrusion of granites and development of pull-apart basins.