In response to the high energy consumption index of the pyro system in the 5,000t/d cement clinker production line, including issues such as high clinker temperature exiting the grate cooler, high CO concentration at the outlet of the decomposition furnace, low heat recovery efficiency of the grate cooler, and low dust collection efficiency of the preheater, this paper proposes a retrofit plan for the preheater system's pressure reduction and capacity expansion, as well as the grate cooler. By taking measures such as expanding the capacity of the decomposition furnace, increasing the inner cylinder height of the C1 cyclone, modifying the connection structure of the C3 cyclone, and lowering the position of the tertiary air duct into the decomposition furnace; changing the fixed grate plate form at the front end of the first section of the grate cooler to an overall structural module for air supply, and designing the grate slot at the front end of the grate plate into a downward flat S-shaped structure, the system pressure reduction effect is significant. After the retrofit, the negative pressure at the outlet of the preheater decreased from 5 300Pa to 4 750Pa, the dust collection efficiency of the system increased to 95.6%, the standard coal consumption of clinker decreased by 3.4kg/t.cl, and the temperature of clinker exiting the grate cooler decreased by about 50°C, achieving the expected retrofit effect.