Abstract: An experimental platform was established to study fine particles distribution and motion characteristics in electrostatic precipitator. The real-time concentrations of fine particles in the ESP with/without water film was tested by the reformed ELPI. The motion characteristics of fine particles such as distribution, trajectory, deposition, classification efficiency and mechanical behavior were analyzed based on the force analysis of fine particles. The results show that the water film has a remarkable influence on the mechanical behavior of fine particles in the near-wall region of the ESP, the electric field force, thermophoretic, concentration gradient force increase respectively, and the interaction between particles and dust collector convert to a diffusion process between gas-solid two phase flow and the water film. Even though with/without water film, both of the concentrations of fine particles show a decreasing trend from the center to the wall in the ESP, the gradient of the cross section increases（especially near-wall region）and the low concentration region near the wall increases with the development of the air flow after water film distributed evenly in the wall. Concentration changes of particles in the range of 0.1-1mm result in a change of that along the way after water film distributed evenly in the wall, and the maximum magnitude of reducing is 30%. Thecurves of the classification removal efficiency of fine particles are similar with/without water film. The removal efficiency is minimal at the particle size of 0.3μm,and when particle size decreased or increased, the particle removal efficiency will increase rapidly. Compared to without water film, the removal efficiency with water film for small particles is increased by 20%.