The invention provides a pre-heat treatment process method of a 35CrMoV ionic nitrided gear for a compressor. The pre-heat treatment process method comprises the following processes: rough machining drawing design; normalizing treatment; quenching treatment; annealing treatment; stabilizing treatment; and the like. According to the pre-heat treatment process method provided by the invention, the hardness of the 35CrMoV gear can reach HB 303-341 through the optimization of process parameters and the improvement on the rough machining drawing design; according to the gear standard of American Gear Manufacturers Association (AGMA), the allowable yield strength of the 35CrMoV gear can be improved by 33.6%, the allowable bending stress can be improved by 10%, the allowable contact stress can beimproved by about 10% from the level 2 to the level 3, and the minimum hardened layer depth can be reduced by 16.7% as required; furthermore, the carrying capacity of the 35CrMoV gear, the contact fatigue strength and the bending fatigue strength can be greatly improved; part of the surface hardening treatment of a carburized-quenched gear can be replaced; and the problem about the distortion ofthe carburized-quenched gear can be solved.