The structure, installation position, working principle and operation method of the heat shield are described. After using the heat shield, the temperature of the secondary air and the tertiary air is greatly improved, the heat recovery efficiency has been significantly improved, the temperature of waste heat is reduced, and the natural gas can be saved by 3 875 598m3 each year. The negative pressure of the kiln hood is basically stable at the fluctuation range of -55~-45Pa.