Air atomization spraying technology plays an important role in mobile phone screen waterproof, oilproof, fingerprint proof coating, explosionproof coating spraying and other technologies. In order to improve the spraying stability and coating uniformity of mobile phone glass screen waterproof coating, simulation analysis and research on the spraying flow field characteristics of air atomization spray gun was carried out. KA-2 automatic spray gun of a nano coating machine was disassembled, the threedimensional model of the spray gun was established according to the measured data and the physical part shape of the spray gun. Using the Fluent software, the twophase flow physical model of the atomization flow field was established, the VOF-DPM model was used to analyze the interaction in gas phase and liquid phase, the atomization pressure and sectoral control pressure were changed to research the air velocity change and flow field distribution by CFD simulation analysis. It is concluded that when the sectoral control pressure is within 0.02~0.04 MPa and the atomizing air pressure is within 0.10~0.15 MPa, spray pattern is best.