Molten salt heat storage system is the key point of solar thermal power station, which has important influence on the safety, reliability and operation cost of power generation system. Based on the analysis of the two element nitrate melt physicochemical properties, the material selection, corrosion resistance, thermal insulation, tank foundation insulation method of the high and low temperature molten salt tank were systematically studied. The optimum design scheme of molten salt tank was given from the angle of technical economy.