In this study, a numerical analysis was performed inside the exhaust pipe to install the electrostatic precipitator in the exhaust pipe. For the experimental conditions, the engine load of 75% with the most severe load was selected in ISO 8178 E3 mode. The internal flow rate of 11 cases was selected to determine the final flow velocity of the electrostatic precipitator chamber according to the fine dust collection type. The exhaust gas of the diesel engine was applied as the working fluid inside the dust collector, and a numerical analysis was conducted based on the flow rate of the exhaust gas. The numerical analysis was performed for 11 cases by the inlet flow rate as in the experiment, and the velocity at 2,000 mm away from the inlet was confirmed. The numerical analysis confirmed that the flow uniformity achieved 0.9 at 100 mm after passing the baffle under all flow conditions. Based on the experimental and numerical analysis results, the design variable factors were confirmed, and the technology for developing the chamber under optimal conditions was secured.