The invention discloses a building thermal insulation mortar material taking vanadium-titanium magnet tailings as a raw material as well as a preparation method and application of the building thermalinsulation mortar material. The thermal insulation mortar comprises the following raw materials in parts by weight: 30-40 parts of vanadium-titanium magnet tailings, 100-120 parts of cement, 10-30 parts of glass beads, 15-20 parts of gypsum, 3-5 parts of sodium carboxymethyl starch, 2-4 parts of allyl isothiocyanate, 5-8 parts of diallyl sulfide, 5-8 parts of sodium lauryl sulfate, 2-4 parts of lithium hydroxide, 6-8 parts of sodium hydroxide, 5-10 parts of kanuma soil, 1-2 parts of water glass and 8-12 parts of an air entraining agent. According to the invention, through reasonable design ofthe raw materials and the ratio thereof and synergistic effect of the raw materials, the thermal insulation mortar can be ensured to have good thermal insulation performance, waterproof performance and fireproof performance, and the workability and crack resistance of the thermal insulation mortar can be improved, so that the use effect of the thermal insulation mortar is improved; therefore, thethermal insulation mortar is more suitable for internal and external wall thermal insulation systems of buildings and has good social and economic benefits.