The pyro system of a 5 500t/d cement clinker production line had problems such as too high pressure loss at the outlet of the C1 cyclone, the inverted temperature of the calciner and the C5 cyclone, the too large consumption of denitrification ammonia, and the low heat recovery efficiency. By technical measures including expanding the volume of the calciner, expanding the space for decomposition, combustion, denitrification, replacing the cone of the C4 cyclone with a crooked cone, using the burner with a new swirl type, optimizing the splash device, improving the cyclone structure, and using nanometer heat insulation as well as the fourth-generation grate cooler, it reduced the coal consumption, power consumption and denitrification ammonia consumption, and the annual comprehensive economic benefit can reach more than 20 million yuan.