For mass concrete with the admixtures of limestone powder and water quenched iron slag (shortly called double admixture concrete) in dam of Jinghong hydropower station located at the downstream of Lancang river in Yunnan province, the mineral composition of double admixture was analyzed in this paper. And it is also studied by materials testing and microscopic analysis methods such as laser particle analysis, scanning electron microscopy, energy spectrum analysis, X-ray diffraction analysis and thermo gravimetric-differential thermal analysis that the hydration, hydrated product and mechanism of hydration process in the system of cementing and double admixture material system. Then the mechanical, thermal and deformation properties and the durability of the concrete with double admixtures were also analyzed by experimental methods. The study results show it was theoretically feasible that adopting the double admixtures as the admixture of the mass hydraulic concrete which can be roller compacted concrete or normal concrete. And the properties of the double admixture concrete in Jinghong hydropower station meet all kind requirements.