Abstract: The connection of wind tunnel and return air shaft has always been a mining ventilation research focus. The right angle connector has been widely applied by ventilation systems. After a right-angle turn, the airflow enters the straight fan chamber, which is required to reach a certain length for a stable wind speed and airflow field. This paper studies the length of stable section under different fan chamber diameters and roughness by simulating its flow field with FLUENT. The optimization measures, including transforming the inside and outside right angles into the are shape and adding the number of wind guiding vanes, are put forward to efficiently reduce local resistance at the corner. The required length for the stable section is greatly reduced, which indirectly generates economic benefits for the mining industry.