Abstract: In order to effectively suppress spontaneous combustion of residual coal at 5242 fully mechanized caving face gob and to make sealing fire zone get effective control, by analyzing the causes of spontaneous combustion and control difficulties of sealing fire zone, we find the mined-out area ignition range. Using the original return airway and new technology roadway, three-phase foam and other fire prevention materials are injected into mined-out area, and the fire zone is effectively controlled. At the same time, by sampling gas analysis, O₂ concentration is below 5% and CO concentration reduces to 10×10^-6. The technology controls the sealing fire zone effectively and eliminates the potential hazards, which provides a guarantee for unsealing working face smoothly.