Numerical analysis was conducted to characterize the particle charging quantities in the charging cell of a 2-stage parallel-plate electrostatic precipitator with respect to particle size. The numerical method took into consideration of particle charging rate equations and particle equations of motion, allowing the locally varying non-uniform electric field and ion number concentration along the particle trajectory. The charging rate model developed by Lawless(1996) was used in the present study. According to the present study, the numerical results showed good agreement with the available experimental data. Keywords : 2-Stage Parallel-Plate Electrostatic Precipitator(ESP), Particle Charging, Collection Efficiency, DOS Aerosol, Numerical Analysis