Abstract: A high strength plugging agent was developed according to the injection sol breakthrough along high permeability formation or bigger hole in the testing of SMD sol in T-7 block in Shengli Oilfield. The plugging agent is inorganic gel agent mainly made from fire mineral powder. It is suspend serum before flooding into formation. Under the temperature of formation, it could production high intensity gel after a certainty time, so it can plug the high permeability formation or bigger hole. The better effect was gained after 4 wells’ field test.