When water droplets precipitate under the action of gravity and frictional forces, they will collide with smaller aerosol particles and fall to the ground. Usually, either droplets or aerosol particles carry some electric charges, and some may be highly charged. Therefore, the electrostatic effect is a very important factor in particle scavenging. Wet scrubbers as air pollution control devices use the same theory as scavenging to remove both particulate and gas contaminants from the industrial exhaust streams. Electrostatic wet scrubbers were developed in an attempt to improve collection efficiency by raising the attraction force between droplets and particles. Very few numerical models have been developed to describe the phenomenon of particle collection by highly charged droplets when electrostatic force is dominant. In an attempt to understand the physics of scavenging, a new three-dimensional model has been developed to simulate neutral or charged particles collected by a group of neutral or charged droplets. The model can simulate the particle traveling through a matrix of droplets. Both the inertial effect and the electrostatic effect on particle scavenging have been considered. The collection efficiency can be estimated by utilizing this developed model. The effect on the collection efficiency by the size of the particle and of the droplet, the charges of the particle the droplet, and droplet distance have been investigated. A validation approach has also been developed and the study results have achieved good agreement with published data.