The Central Asian Orogenic System (CAOS) is one of the largest accretionary orogenic belts characterized by the highest rate of Phanerozoic continental growth in the world. In recent years, extensive studies of the orogenic belts have been conducted, focused mainly on Paleozoic accretionary processes and granitic magmatism. By contrast, Mesozoic magmatism and tectonism are poorly understood. This paper tries to analyze and discuss temporal-spatial distribution and tectonic setting of the early Mesozoic granite magmatism. According to zircon U-Pb ages, the Early Mesozoic granitoids in the middle-south segment of the Central Asian Orogenic System can be roughly divided into two stages, i.e., early-middle Triassic (251～227 Ma) and late Triassic-early Jurassic (226～195 Ma). The early-middle Triassic rocks consist mainly of the monzogranite-granodiorite_syenite assemblage. These granitoids are distributed in such areas as the east-middle part of the East Tianshan orogenic belt, the north-middle part of the Beishan orogenic belt, the central Mongolian block, the western part of the Altay orogenic belt and the middle-western region of the Inner Mongolia-Jilin orogenic belt. They are spread along or near the suture zones. The granitoids have metaluminous-weakly peraluminous, calc-alkaline-high-K calc-alkaline or weak alkaline features. I-, S- and A-type or I-A type granites are all exposed. Some ultramafic-mafic rocks are associated with these granitoids. The late stage rocks widely occurring in every orogenic belt are composed of the alkali feldspar granite-K-feldspar granite-monzogranite-alkali feldspar quartz syenite assemblage. They are characterized by metaluminous-wealy peraluminum, high-K calc-alkaline or alkaline granites. Most of them are of A-type and I-A type. Some of them have the characteristics of highly fractionated I-type granites. There exist voluminous coeval ultramafic-mafic rocks. The early-middle Triassic granitoids have a higher ΣREE content, while the late ones have a significant negative Eu anomaly and are more depleted in Ba, Nb, Sr, P and Ti. The Sr-Nd isotopic characteristics reveal that the granitoids in the northern margin of the North China Craton show very low εNd（t） values (-19.6～-5.4) and the old tDM values (1.23～2.09 Ga), suggesting derivation from an ancient continental crust: those in the north Mongolia-west Transbaikalia orogenic belt and Inner Mongolia-Jilin orogenic belt were derived from a young source, whereas those in central Mongolian block, Altay orogenic belt, East Tianshan orogenic belt and Beishan orogenic belt were derived from an ancient micro-continental crust with some contributions of young mantle-derived components. In general, the early-middle Triassic granitoids were derived from dual-sources, while the late Triassic-early Jurassic granitoids mainly from the mantle source. Mantle-derived components have an increasing trend from early to late ones. Juvenile compositions of major sources for the granitoids were distributed in the Okhotsk belt and its adjacent areas, and also contributed by the ancient continental crust through underplating of young mantle-derived magma, leading to vertical continental growth in the post-orogenic or post-collision stage. According to recent researches, the early-middle Triassic granitoids in the eastern and western regions show some differences in tectonic settings. The north Mongolia-west Transbaikalia orogenic belt seems to show an intraplate tectonic setting of the continental rift. The central Mongolian block may represent the late stage of the syn-orogenic setting. The Altay orogen and the East Tianshan orogen are described as a post-orogenic extensional setting. The Beishan orogen reflects the late orogenic collision or post-orogenic tectonic setting. The Inner Mongolia-Jilin orogenic belt has the syn-orogenic characteristics. The late Triassic granitoids mainly reflect a post-orogenic, non-orogenic or intraplate extensional tectonic setting.