The invention discloses a heat insulation anti-sticking coating for mechanical cast steel machining and a preparation method of the heat insulation anti-sticking coating. The preparation method comprises the steps of weighing magnesia powder, meta-barium borate, water glass, N-methyl-2-pyrrolidinone, activated bentonite, dimethyl formamide, magnesium chloride, xylene, barium chloride, polytetrafluoroethylene, polyimide, ethyl acetate, aluminum paste and paint, feeding magnesia powder, activated bentonite and barium chloride into an edge runner, performing dry mixing, and adding water glass for mixed grinding; feeding polyimide, polytetrafluoroethylene, xylene, ethyl acetate and dimethyl formamide into a reaction kettle for uniform mixing to obtain a mixture, mixing the mixture with the mixed-ground raw materials, adding the rest of the raw materials, grinding the raw materials in a three-roller machine, and adjusting the viscosity. The relative density of a product is 16-18, and the product can be solidified at low temperature; the product can resist high temperature of 1,000-1,200 DEG C, cannot be separated, does not corrode metal equipment, protects steel materials from being oxidized, avoids decarbonization and can be widely produced to continuously replace the conventional material.