In the hydrochloric acid regeneration system of a cold rolling steel plant, the large amounts of hydrochloric acid droplets and iron oxide dust in the flue gas at the absorption column outlet cause serious air pollution. To reduce pollution, a high-precision cyclone separator is utilized to recycle hydrogen chloride acid mist and iron oxide dust simultaneously. The key factors of the high-precision cyclone separator, such as pressure drop, separation efficiency, and fluid density, are investigated to determine the optimal operation parameters under practical working conditions. Results show that the separation efficiency of the cyclone separator increases rapidly initially and then decreases gradually with an increase in pressure drop. Pressure drop and separation efficiency increase slightly with an increase in inlet fluid concentration. When the velocities of the inlet gas are 4.8–10 m s–1 and 5.0–9.2 m s–1, the separation efficiencies of hydrochloric acid and iron oxide are both higher than 80%. When the velocity of the inlet gas is 6.67 m s–1, the separation efficiencies of hydrochloric acid and iron oxide reach the highest values of 92% and 89%, respectively.