Abstract: Hydrogen, as a flexible carrier of renewable energy, is investigated for its potential to facilitate a low-carbon transition in the cement industry through coupling with alternative fuels. To address the technical bottlenecks associated with hydrogen combustion in cement kilns, a pilot-scale platform was established by taking fuel properties and thermal characteristics into account. The platform enabled the validation of a cross-scale model bridging microscopic hydrogen radical effects with macroscopic energy transfer. Calcination experiments using hydrogen-coupled multi-source alternative fuels were conducted with blending ratios ranging from 0% to 70% by calorific value, covering diesel, lean coal, rice husk, rubber powder, and wood powder. These experiments established a technical pathway for significantly reducing fossil fuel consumption through the optimized combustion of hydrogen-coupled alternative fuels. The results demonstrate that the high reactivity of hydrogen effectively promotes the combustion of low-quality fuels, with the enhancement being more pronounced for fuels with lower calorific values and fixed carbon contents than for high-quality fuels. Based on a comprehensive evaluation of flame morphology, flame temperature, and flue gas emissions (CO and NO_x), pilot-scale studies revealed that the hydrogen co-firing ratio with diesel should be limited to 24%; for co-firing with rice husk powder and lean coal, the optimal hydrogen ratios should be kept within 15% and 22%, respectively; and for co-firing with rubber powder and wood powder, the hydrogen substitution ratios should be controlled within 12% and 11%, respectively. Notably, the hydrogen injection location significantly influences combustion characteristics and pollutant emissions. Injecting hydrogen directly into the main combustion zone of the calciner leads to rapid oxidation and intense localized oxygen consumption, which temporarily starves the primary reaction region and delays the burnout of coupled fuels. To overcome this limitation, staged hydrogen injection is proposed: introducing a secondary hydrogen stream into the burnout zone enhances the conversion of residual CO to CO₂, thereby improving fuel utilization efficiency and overall carbon performance. Rigorously validated through pilot-scale testing, this hydrogen-coupled alternative fuel calcination technology achieves a substantial carbon emission reduction of 180 kg CO₂ per ton of clinker product while overcoming classical operational hurdles such as ignition difficulty, flame instability, and incomplete burnout. This study provides a practical pathway for decarbonizing the cement industry by integrating hydrogen into existing production systems.