The invention discloses a preparation method of a precoated zirconium sand model for titanium alloy casting, and belongs to the technical field of casting. Firstly, zirconium silicate is taken, crushed and sieved for screening to obtain surface layer zirconium silicate mixed by powder with two particle sizes; and a coupling agent, resins, hexamine and the like are added for mixing, are dried and crushed, are mixed with yttrium oxide, are put in a sand mold forming machine for baking, standing and air drying, are infiltrated in yttrium sol, are sprayed with yttrium oxide and yttrium sol mixed liquid, and are roasted to obtain the precoated zirconium sand model for titanium alloy casting. The zirconium silicate is used as the raw materials, is stable in chemical property, resists high temperature, is infiltrated and sprayed with a layer of yttrium oxide on the surface to make up the defect of easy generation of the interface reaction with a zirconium casting material in casting forming due to higher chemical activity of traditional molten titanium, and is better in mechanical performance and higher in production value.