Monitoring and early warning of coal spontaneous combustion hazards in goafs are essential steps for preventing early-stage coal spontaneous combustion fires, and also core challenges that need to be urgently addressed. To solve the monitoring and early warning problem of coal spontaneous combustion fires during the mining process of the 1502-2 extra-thick steeply inclined fully mechanized caving face in the 5-2 coal seam of Chicheng Coal Mine, a coal spontaneous combustion programmed temperature-rising experiment was used to obtain the variation laws of concentrations of gases such as CO, CO?, CH?, C?H?, C?H?, and C?H? with temperature during the spontaneous combustion and oxidation process of the tested coal samples at different temperatures. Combined with field data, CO and C?H? were determined as the index gases for predicting coal spontaneous combustion, and ΔCO/ΔO? and C?H?/C?H? were taken as the early warning indices for coal spontaneous combustion. A five-level early warning index system of "gray, blue, yellow, orange, red" was proposed, and the early warning thresholds were determined based on field conditions, forming a hierarchical early warning index system for coal spontaneous combustion in fully mechanized mining faces. This hierarchical early warning index system was applied to the 1502-2 fully mechanized mining face in the 5-2 coal seam, achieving early warning of coal spontaneous combustion hazards, improving the technical level of coal spontaneous combustion fire prevention and control, and ensuring the safe mining of the working face.