Abstract: For the commissioning of the WWER nuclear island ventilation system, the fixed flow orifice plate is used for the air volume adjustment, and the on-site operation is heavy and time-consuming. By analyzing the principle of the aperture mechanism, a ventilation flow orifice plate aperture adjuster is developed. The test results show that the regulator realizes the function of changing the diameter of the line to adjust the air volume, and has the characteristics of easy installation and high precision. The device is used for the system commissioning, avoiding the repeated changes of the fixed-diameter orifice plates, which is beneficial to improve the commissioning efficiency, and also provides reference for the design of other stack-type ventilation systems.