Energy-consumption-free arc gate opening/closing device and gate opening/closing method

The invention discloses an energy-consumption-free arc gate opening/closing device and a gate opening/closing method. The arc gate opening/closing device comprises a water distribution tank, a communication water pipe, a communication water pipe valve, a gas discharge hole, a water distribution tank support, a water discharge pipe, and a water discharge pipe valve. According to the energy-consumption-free arc gate opening/closing device, a water tank is arranged in the reverse direction of the gate, after the water tank is full of water, the moment of the self gravity to a hinge shaft is large than the moment of an arc gate to the hinge shaft, when the gate needs to be opened, a water inlet valve is opened, water in a reservoir enters the water tank through the water pipe by virtue of self gravity, and the gate is automatically opened slowly when the moment of the self gravity of the water tank and the gravity of the water in the water tank to the center of the hinge shaft is large than the moment of the arc gate to the hinge shaft; when the gate needs to be closed, water in the water tank is discharged, and the gate is automatically closed slowly when the moment of the self gravity of the water tank and the gravity of the water in the water tank to the center of the hinge shaft is smaller than the moment of the arc gate to the hinge shaft; the energy supply is not needed for opening/closing the gate.