The pyro system of a 5 000t/d cement clinker production line originally used a dual series five stage preheater system, a three jet decomposition furnace, and a third-generation grate cooler with air beams. Due to the long running time of the production line, there are problems in the pyro system, such as high resistance of the preheater system, high outlet temperature of C1, unreasonable air usage of the cooler fans, high clinker temperature at the outlet of the cooler, and low heat recovery efficiency. Based on the on-site thermal diagnosis results of the pyro system, a technical analysis was conducted on the problems encountered during operation, and an optimization plan for the pyro system was developed. Technical transformation was carried out from the adjustment of the spreading device, expansion of the cyclones, expansion of the calciner, replacement of efficient and energy-saving fans, and replacement of the fourth generation grate cooler with middle roller crusher. After the implementation of the technical transformation, the system energy consumption was further reduced, the system resistance was reduced, and the heat exchange efficiency was improved, achieving the expected technical transformation goals.