A numerical calculation model of air-assist boom spraying was established. The Fluent was used to simulate the gas-liquid two phase flow field of air-assist boom spraying when the operational parameters of influencing factors changed, including airflow velocity of air curtain, the horizontal and vertical relative position between the air curtain and the nozzle, and the spraying angle. The results showed that the influence of air curtain on gas-liquid two-phase gradually increased with the increase of airflow velocity of air curtain. The air curtain could be more useful to anti-drift performance when there was a reasonable horizontal distance between the air curtain and the nozzle. Air curtain going away from the nozzle in vertical direction was equivalent to airflow velocity of air curtain decreasing. Therefore, the anti-drift performance went weaker. With the increase of spraying angle, the kinetic energy of droplets in vertical direction decreased. More droplets were difficult to reach the sample surface because of the attenuation of kinetic energy in vertical direction, so that the anti-drift performance went weaker.