Fire resistance of wood samples treated with boron-based wood preservative（D-B-M） were tested by a cone calorimeter.The preservative was a mixture of disodium octoborate tetrahydrate（DOT）,boric acid（BA） and magnesium sulfate（MgSO4）.Testing results indicated that there was a synergistic effect among the mixed components.The heat release rate,total heat release and the yield of CO2 of D-B-M treated samples decreased considerably.