A 2 500t/d cement clinker production line suffered from frequent material collapse, low output, high heat consumption (826kcal/kg.cl), high preheater outlet gas temperature (350°C), and high pressure loss. By adopting upgrading the preheater system(eliminating the material accumulation zone at the C3 inlet, lowering the tertiary air duct entry point, optimizing the dispersion box angle and height); expanding cyclones inlet area; replacing the cooler with a fourth-generation step-grate cooler; and lining microcrystalline plates on the connect section between the calciner and the kiln inlet chamber and so on . After the upgrading, the system operates stably with increased clinker output. The kiln heat consumption decreased to 728kcal/kg.cl (an 11.7% reduction), the preheater outlet gas temperature dropped to 285°C, system pressure drop was reduced by 12.4%, and the outlet clinker temperature decreased to 95°C. Ammonia water consumption was reduced by 21.7%. Overall energy efficiency improved significantly, generating substantial social and economic benefits for the enterprise.