In order to reduce the energy consumption of the local ventilation system for contaminants control, the axial velocity distribution law of the slot side gas-collecting hood under jet action was studied. The influence of exhaust air volume on the dimensionless axial velocity without jet and the flow field characteristics of the gas gathering system under the condition that the jet velocity was equal to the wind speed at the hood were analyzed by numerical simulation. Based on the results of the numerical simulation, the variation laws of wind speed controlled by the jet angle Aj and jet slot length Ls varying in different ranges were compared. The results show that the exhaust air volume does not affect the variation of axial velocity. The velocity attenuation becomes slow when the air supply ejects airflow in the opposite direction of the Aj. When Aj is -10°, the control wind speed reaches the maximum value, whichis 0.76 times of the wind speed at the hood. The optimum value of Ls is 0.4 times the width of the worktable, and Vc= 0.57Ve at this time. When the value of Ls exceeds the above value, the control wind speed will not increase.