To decrease the jet flow rate in contaminants control for a purpose of energy conservation, the flow field characteristics of exhaust flow assisted with a jet was focused. When the angle θ between the jet and the exhaust flow ranges from 90° to 60 °, utilizing the numerical simulation, the conditions to form steady flow was determined and the changes of the centerline velocity and control region of the exhaust flow were studied. Meanwhile, based on simulation results and the analysis of the factors that affect centerline velocity and control region, two calculation methods for the decay of centerline velocity and control region of the exhaust flow with different θ were obtained. The results show that when θ is less than 70°, the steady exhaust flow can not form; when θ ranges from 90° to 70°, the increase rate of the centerline velocity drops with the momentum ratio of the jet and the exhaust flow increasing, while the increase rate of the centerline velocity increases when θ decreases. Thus, the exhaust flow can be enhanced by decreasing θ, which effectively control contaminants. ©, 2015, Science Press. All right reserved.