Hot mill is important equipment in metallurgy industry. As one kind of them, magnesium alloy hot rolling mill can roll magnesium slab whose maximum thickness is 300mm in thermal state horizontally and vertically several times to be plates and strips with ideal thickness. After finishing process, the rolled plates and strips are ready for finished products processing and they can be raw materials for the follow-up cold rolling equipment as well. Magnesium alloy hot mills have various classifications. According to the quantity of rollers, they can be classified into two-roller hot mills and four-roller hot mills. They also can be divided into small-size, medium-size and large-size mills based on specification and be divided into horizontal mills and vertical mills based on the forms of structure. As the earlier enterprise that produced metallurgical mills at home, NHI has provided dozens of hot rolling mill for a variety of companies for years. At present, NHI can produce large-size and medium-size magnesium alloy hot mills of different specifications. In 2013, NHI succeeded in developing the high-performance outfit which is four-roller hot rolling with the widest format of 1725mm. It filled the gap at home and abroad. The key equipment is four-roller magnesium hot mills with high stiffness and high load which won the national invention patent. NHI is a domestic enterprise that has mastered all the techniques of research and development, design, production and commissioning of magnesiumalloy hot rolling mill. It leads an important position in the research and development field of domestic magnesium alloy production equipment.