Low-temperature metallurgy is to study the theories and methods of accelerating reduction of iron ore at a lower temperature by refining iron ore, using catalyst and other means, and provide theoretical basis for the development of the alternative ironmaking process with low energy consumption, low carbon emission, and high efficiency. The research results of low-temperature reduction theory including: fine iron ores have nanograins; energy storage of fine iron ore can improve the utilization efficiency of reducing gas; reaction efficiency can be improved by size refining; the reaction rate can be increased with catalyst; the transmission conditions of the low-temperature reaction are improved; the fluidization mechanism of the multi-stage circulating fluidized bed is studied; and iron nuggets are smelted at a lower temperature. The new technologies of the low-temperature metallurgy including: the improved smelting reduction ironmaking process; low-temperature reduction process of high-quality sponge iron and iron nuggets. Low-temperature reduction process is expected to achieve the energy saving, low-carbon, efficient and low-cost metallurgy, and can be applied to the comprehensive utilization of low-grade iron ore, ferrous metallurgical slag, red mud and vanadium titano magnetite, ilmenite, etc.