One-way overpressure locking valve and auxiliary water tank

The invention discloses a one-way overpressure locking valve. The one-way overpressure locking valve comprises a valve body. A first port, a pressure cavity and a second port which are communicated are sequentially formed in the valve body. A valve plug capable of sliding relative to the pressure cavity and a pre-compressed second spring are arranged in the pressure cavity. One end of the second spring makes contact with the valve plug, and the other end of the second spring is fixed relative to the pressure cavity. The valve body is further provided with a bypass pipeline. An inlet and an outlet of the bypass pipeline are communicated with the pressure cavity. When the valve plug is located between the inlet and the outlet, the first port and the second port are communicated through the bypass pipeline. When the valve plug is moved to close the inlet or the outlet, or when the inlet and the outlet are both located in one side of the valve plug, the first port and the second port are not communicated. The invention further discloses an auxiliary water tank with the one-way overpressure locking valve. The purposes of fluid one-way flow and overpressure closure can be achieved.