The invention relates to the technical field of valve devices, in particular to a
check valve which comprises a sealing shell, a valve element, a valve element, a valve element, a valve element, a valve element, a valve element, a valve element, a valve element, a valve element and a valve element, and is characterized in that a fluid inlet and a fluid outlet are formed in the sealing shell; the valve clack
assembly is fixedly mounted on the rotating pin shaft, and the valve clack
assembly has a first state for blocking the fluid inlet and a second state for swinging around the rotating pin shaft to open the fluid inlet; the indicating
assembly is installed at the end, extending out of the sealing shell, of the rotating pin shaft, and a
signal transmitting piece is arranged in the indicating assembly. In the action process of the valve clack assembly, the rotating pin shaft rotates at the same time, and then the indicating assembly located on the outer side of the sealing shell is driven to act together, so that the
signal transmitting piece can transmit the state of the indicating assembly into an external control chamber in real time, and the state of the indicating assembly corresponds to the state of the valve clack assembly one to one; therefore, the state of the valve clack assembly can be known, and the on-off state of the
check valve can be fed back in real time.