The clinker production line experienced issues in the kiln system's grate cooler, including significant fluctuations in the secondary air temperature entering the kiln and the tertiary air temperature entering the precalciner, high coal consumption, and frequent burnout of the "cross bars" in the first section of the grate cooler. Analysis revealed that unstable material flow on the fixed grate bed was the primary cause. The proposed solutions included reducing the terrace height between the fixed grate and the horizontal grate, adjusting the step height, and rotating the entire fixed grate bed. After the modification, the material flow has become stable, the rapid cooling effect has been improved. The secondary and tertiary air temperatures have significantly increased with reduced fluctuations, coal consumption has decreased, the burnout issue of the "cross bars" has been largely resolved, the quality of clinker has been enhanced. The modification has achieved the expected objectives, effectively stabilizing the thermal regime of the kiln system, yielding remarkable economic benefits.