The invention discloses an early-strength quick-drying refractory mud filling material with a good insulativity. The filling material is prepared through the following steps: adding water in 100 parts of main raw material and 1-10 parts of composite additives, mixing, ageing mixture or fermenting, grouting, naturally drying and baking, wherein the main raw material is a mixture of sintered mullite, quartz sand powder, alumina micropowder and pure calcium aluminate cement; and the composite additives are lignosulfonate, sodium carboxymethylcellulose and one substance or a mixture of two substances selected from subnano alumina micropowder with a grain size of 0.25-0.50 mu m, silicon micropowder with a grain size of 1-2 mu m, sodium tripolyphosphate, sodium hexametaphosphate and sodium polyphosphate. The filling material has good properties such as good early strength, rapid consolidation speed, no moisture regain and good insulativity, dose not corrode metals, can be widely applied to a metallurgy smelting high temperature sensor and a rapid temperature-measuring element to be used as an insulation material.