The efficient removal of fine dust from exhaust gas reduces the harm to human health and minimizes material waste. A circumfluent cyclone (CFC) was designed to perform with increased gas-solid separation efficiency and decreased pressure drop compared to conventional cyclone separators, and its flow pattern and velocity distribution were investigated. Commercial computational fluid dynamics software was used to simulate the 3D-gas-flow field using the Reynolds stress model (RSM). The simulation results (e.g., for the velocity profile, pressure drop, and separation efficiency) were in good agreement with the experimental results and indicated that about 78% of the gas flows directly out of the CFC through the inner cylinder and then the vortex finder, which significantly shortens the cleaned gas flow path and thereby reduces friction loss. The CFC also decreases the shortcut flow rate near the vortex finder entrance, reducing particle escape. Finally, the discrete particle model (DPM) was used to predict the flow pattern of particles of different sizes.