The invention relates to a silicon-titanium alloy film coat of an air preheater tube and an electrostatic spraying process thereof, and belongs to the electrostatic spraying technology of an environment-friendly, energy-saving and efficient silicon-titanium alloy film air preheater tube. Main components of the coat comprise SiO2, NiO, B2O3, TiO2, Pb2O3, NaO2 and K2O. A preparation method for the coat comprises the following steps: mixing and crushing common silicon-titanium alloy power and K2O to charge the powder, spraying the mixture to an air preheater steel tube under the high pressure of 30 to 120KV by using a positioning gun, heating and cooling the steel tube, and cushioning a high-temperature pad to obtain the coat. The process can realize automatic powder spraying, does not need manpower, obtains workpieces with unlimited lengths, and has the characteristics of environmental protection, energy conservation and high efficiency; due to the addition of K2O, the atomization is stable, the film is coated uniformly, the mass density is high and the thickness is controllable; the manpower and spraying cost are saved, and the service life is prolonged; and the prepared coat is superior to that in a common enamel process and a plastic powder electrostatic spraying process on the aspects of mechanical strength, adhesive force, high temperature resistance, abrasion resistance, acid and alkali corrosion resistance, ageing resistance and the like.