A 2D3V Particle-In-Cell (PIC) and Monte-Carlo Collision (MCC) model is adopted to simulate the plasma parameters and the channel wall erosion depth of a Hall thruster. Ions and electrons are modeled as particles. Artificial mass ratio and permittivity are employed to simulate the electrons and ions simultaneously. The influence of the magnetic topology on the erosion of the channel walls is discussed. The erosion model is based on the distributions of ion energy and incidence angle and the sputtering yield function at the channel wall. Simulation results are compared with experimental data.