Abstract: 3 large ore fields including 13 ore deposits and a large number of ore occurrences are clustering in Dexing densely ore deposited area, which is 20 km long and 10 km wide. The regional tectonic evolution, magmatism , as well as the metallogany are controlled by the NE trending Jiangxi deep-seated fault belt. The formation of Dexing densely ore deposited area is the result of a unified geologic process of tectonism, magmatism and metallogensis. The large scale polymetallic mineralization is mainly controlled by the deep-sourced magmatism. The Precambrian and Mesozoic magmatisms were closely related to mineralizations. The ore-bearing formations and source beds of Shuangqiaoshan group with a thickness of 15 km of the Meo-Neoproterozoic age were formed by submarine volcanic eruptions. The large scale marine intermediate-basic volcanic eruptions produced a great quantity of spilite (basaltic)-keratophyre (andesitic) volcanics and pyroclastic rocks which would have carded abundant Cu, Mo, Pb, Zn, Au and Ag from upper mantle and lower crust to the upper crust. The concentration of ore-forming elements in these horizons suggests that they could be the source beds. The large scale regional I-type granitoids were formed in the Mesozoic. Petrological study supports the following model: The magma was originated from basic “amphibolite-gabbro” at the deep crust(depth>27km), in which 40％ magma with granodiorite composition was melted from the lower crust and partially assimilated by the “sial-sphere” material in upper crust during the magma rising and evolved into the magma enriched in K2O and H2O. The rock in magma source area contains a great quantity of Cu, Mo, Pb, Zn, Au and Ag, as well as the minerals abundant in H2O such as amphibole and micas. The sialic upper crust is the basement of Shuangqiaoshan Group and is also enriched in Cu, Pb, Zn, Au, Ag an d minerals abundant in H20 such as chlorite and sericite. Consequently, the composition of the magma am placing into the shallow crust was more baundant in ore-forming elements and H2O. The constraints of I-type granite in Mesozoic to the metallogeny are at least in five aspects: (1)supply ore-forming metal elements such as Cu. Pb, Zn, Au and Ag; (2)supply hydrothermal fluids; (3)supply heat energy; (4)provide space for ore deposits; (5)activate the ore-forming materials from adjacent rocks and prompt mineralizations.