Abstract: For the common polyurethane grouting material, the curing reaction temperature is high, there are hidden dangers such as smoke and coal spontaneous combustion the grouting process the mine.On the basis of the addition of nano-scale fly ash as the aggregate, NH₄Al (SO₄) ₂·12H₂O selected respectively combined with polyether polyol GR4110B and other additives to form A component Ba (OH) ₂·8H₂O and polyether polyol TMN450 to form B component, isocyanate as C component A novel cooling polyurethane-nano fly ash grouting material was prepared by the original polymerization method.At the same time of achieving significant cooling effect, the optimal compounding ratio between crystalline hydrated salt, nano-powder ash and polyurethane was studied.On this basis, combined with partial characterization methods its microstructural composition and its cooling mechanism.The results show that the two inorganic materials can be effectively filled into the polyurethane matrix to form an organic/inorganic compound.When the nano fly ash content is 40% and the inorganic hydrated salt content is 10%, the optimal compressive strength is 44 MPa, the maximum curing temperature was reduced to 82℃ n addition, by SEM and infrared spectroscopy analysis, the incorporation of inorganic hydrated salt promoted the in the system and the ammonia molecule produced after the reaction form NH₂, and successively formed the isocyanate reacted to form a substituted urea t was observed that the cross section of the material contained many solid microbeads and small pores gaps between, and soluble salts were dissolved in the slits.Thermogravimetry and mechanism analysis further verified that the nano fly ash in the composite reaction system reached the first cooling process by heat conduction endothermic he chemical reaction of Ba (OH) ₂·8H₂O crystallization water with thermal vaporization and NH₄Cl is the main stage to limit the temperature the system NH₄Al (SO₄) ₂·12H₂O dehydration vaporization endotherm and phase change, reciprocating absorption dehydration vaporization endotherm with soluble salts such as BaCl₂ in the gap is the final stage to lower the temperature of the reaction system.