Large amounts of high-temperature gases were generated in ironmaking plant and ideal acceptable hood above the heat source was not installed affected by process conditions. At the top of the exhaust hood， dust easily escaped because of thermal plume.Based on the test data of dust composition and size distribution in ironmaking plant， numerical models suitable for high-temperature dust gases were established and key boundary conditions for the gas-solid two-phase flow under high-temperature conditions were determined.The study shows velocity decay of convergence field is sharp at the suction outlet and thermal plume is strong in the exhaust hood. The control method of pressure distribution and the key factor to prevent high-temperature dust escaping are proposed in the exhaust hood. Optimized design and engineering practice of the exhaust hood are given when the suction outlet is on the side after analyzing the flow field resulted from coupling effect of thermal plume and ventilation airflow.