Airflow field and effective region for pollution discharge was predicted around a circular flanged exhaust opening in a cubic room without window,three different turbulent models were employed to simulate airflow field near the exhaust inlet indoor,SIMPLE algorithm,standard wall function and pressure condition was chosen,and experiment data from Furio Cascetta at Reynolds number 6.812×104 was selected to verify simulation results.Main focus was on profile of velocity magnitude at air speed,2m/s and 0.3m/s,in a condition average cross-section velocity of the exhaust opening and diameter of the opening being 5.96m/s,0.173m,respectively.Numerical results show that air velocity decreases gradually in radial direction and axis direction away from origin,and changes most dramatically at corner of the opening.Projection of velocity contour surfaces resembles a semiellipse with major axis in radial direction on vertical and symmetrical plane at a higher air velocity,it however approaches a hemisphere of greater radius gradually when air velocity decreases; at 2m/s,major axis of the projection semiellipse was 0.70 times the diameter of the exhaust opening,while the minor axis seems to be 0.45 times the diameter and at 0.3m/s,the major axis of the projection semiellipse becomes 1.60 times the diameter,while minor axis turning into 1.55 times in vertical and symmetrical plane; The effective region for pollution discharge is similar to contour surface of velocity magnitude,like a semiellipsoid,at 0.3m/s air velocity.