Abstract: Based on the theory of non-steady electrostatic collection of charged particles, the particle migration velocity during the non-steady collection was calculated. According to the mass transfer theory of turbulent flow, an expression of turbulent mixing-diffusing coefficient was derived, and a new boundary condition at counter electrode was deduced on the basis of boundary layer theory. Then, the 2-D turbulent mixing-diffusing equation of particles during non-steady electrostatic dust collection was given in difference scheme by the finite difference method and stepwise super-relaxation iteration method. With the numerical simulation carried out by Matlab, how the mass concentration of dust particles are distributed at different time during non-steady dust collection by ESP (electrastatic precipitator) was obtained, as well as the dust classification efficiency in accordance to the sectional distribution of mass concentration. The comparison between measured and simulated results of different sectional dust concentrations showed that they conform well with each other. A conclusion is thus drawn that the dust collection efficiency calculated in this way is more accurate than that by conventional theoretical calculation.