A bypass valve comprises a valve body (1) which has a gas inlet and a gas outlet, wherein a check valve (4) is provided at the gas outlet. The check valve (4) comprises a check valve body (41), a ventilation plate (42) and a first sealing gasket (43). A first gas passage (411) for gas delivering is provided within the check valve body (41). Ventilation holes (421) are provided on the ventilation plate (42), the ventilation holes being in communication with the gas outlet. The first sealing gasket (43) is provided between the ventilation plate (42) and the check valve body (41), and the first gas passage (411) and the ventilation holes (421) are in selective communication with each other via the first sealing gasket (43). Stepwise annular grooves comprising a first annular groove (14) and a second annular groove (15) are arranged on the valve body (1) at the gas outlet. The ventilation plate (42) is arranged in the first annular groove (14). The check valve body (41) is arranged adjacent to the outer side face of the ventilation plate (42) and fixed to the valve body (1) of the bypass valve by a screw. A sealing ring (5) is arranged in a connection joint between the ventilation plate (42) and the valve body (1) of the bypass valve, and one more sealing ring is arranged in a connection joint between the check valve body (4) and the valve body (1) of the bypass valve. The check valve (4) is provided in the gas outlet in the bypass valve, causing the direction of the gas flow to be unique, overcoming the problem of imprecise concentration of the anaesthetic gas caused by the a gas backflow. Furthermore, the provided bypass valve has more simple structural technology and better gas tightness.Перепускной клапан содержит корпус (1) с газовпускным отверстием и газовыпускным отверстием для выпуска газа, у которого установлен обратный клапан (4). Обратный клапан (4) содержит корпус (41), вентиляционную пластину (42) и первую уплотнительную прокладку (43). В корпусе (41) обрат
