Synthetic film resistor is the key component of synthetic film potentiometer, and the linearity of synthetic film resistor directly determines the accuracy of the potentiometer. Spraying is the key machining process of synthetic film potentiometer manufacturing because spraying uniformity has crucial influence on the linearity of resistance. Factors that affect the spraying uniformity are the uniformity of atomization, the uniformity of relative speed between spray gun and synthetic film resistorand the distribution characteristics of the spray chamber flow field, etc. In this paper, the atomization of toluene was analyzed, and how air pressure, mass flow rate of toluene and spray distance influence the atomization uniformity was obtained. For the spray gun with nozzle diameter of 05 mm, when the flow rate of toluene is constant and air pressure gets increased from 0.2 MPa to 0.4 MPa, the distance between the uniform atomization area and nozzle is in the range from 260 mm to 150 mm. When the air pressure is constant, mass flow rate of toluene gets increased from 1.89×10-5 kg/s to 4.89×10-5 kg/s, the distance between uniform atomization area and nozzle is in the range from 130 mm to 200 mm.