<p>This work examines how the axial length of collecting plates influences particle collection performance in a two-stage electrostatic precipitator (ESP), with particular attention to particle charging characteristics. Numerical simulations were conducted to resolve the coupled gas flow, electric field, and particle motion under various geometric configurations and operating conditions. The distributions of electric potential, ion charge density, flow velocity, and particle trajectories were systematically analyzed to clarify the underlying mechanisms governing particle capture. By separating the ESP into distinct charging and collecting regions, electrohydrodynamic (EHD) flow effects were effectively suppressed, allowing particle collection to be governed primarily by the charge acquired in the charger and the electric field established in the collector. The results demonstrate that collector length plays a critical role by controlling particle residence time within the collection region, whereas the influence of charger length on overall performance is limited once sufficient particle charging is achieved. Consequently, extending the collector while appropriately reducing the charger length is shown to be an effective strategy for enhancing the performance of two-stage ESPs.</p>