The alkaline-resistant brick is made of silica and flint clay composed with some additive to improve the microstructure, reacting with alkaline oxide and generating one kind high viscosity glass phase covering the brick surface to block the air hole to keep the permeation from alkaline slag to achieve the purpose of erosion resistance from alkali. This product has the characteristics of volume stability, anti-erosion and penetration-resistance, widely used for cement kiln as preheater, decomposing furnace and tertiary air duct etc.