The machining and environmental performance of composite electrostatic spraying (CES) largely depends on the effective transport of droplets to the machining zone. In this study, a numerical model of droplet transport process in CES milling was established by using COMSOL Multiphysics software to evaluate the droplet transport by the droplet volume reaching the tool target area and the droplet transport efficiency. The droplet transport process in CES milling under different voltages, flow rates of inner and outer fluids, and spindle rotational speeds was numerically analyzed. The cutting force and cutting temperature obtained from milling experiment were employed to verify the numerical analysis results of droplet transport. The results show that increasing the voltage and flow rate of inner fluid could increase the droplet transport efficiency and droplet volume reaching the tool target area. However, increase in the flow rate of outer fluid and spindle rotational speed tended to reduce the droplet transport efficiency and droplet volume reaching the tool target area, in particular, when the spindle rotational speed was increased from 1200 to 5000 r/min.