The lower part of a key project of oil tank area is backfilled by overburden from open pit mining for more than 30 years with different level of gas discharging, heat generating and self-ignition. Treatment should be done to the deep sealed fire zone of the oil tank area to ensure the safety of the upper proposed oil tank. Analysis is made on the advantages and disadvantages of grouting methods; by the comparison of different schemes, compaction grouting with water, fly ash and paralysant was adopted with good effect. The paper introduces the grouting design, construction process and the grouting effect.