To meet severer working conditions of heating furnaces, mullite based castables are updated by adopting high purity binding system to improve refractoriness under load. They have brought about reduced deformation during long-term service at high temperature higher loading ability and longer service life. They have been adopted in many heating furnaces of Shoudu I & S Co., Wuhan I & S Co., Tangshan Guofeng I & S Co., Jiangyin Xingcheng Special Steel Co., etc. They have also been adopted in magnesium reduction furnace, with greatly improved service life, 5~8 times that of the previous brick linings.