Air pressure self-balancing check valve

The invention discloses an air pressure self-balancing check valve used for liquid drainage of a well liquid gaining machine with a gas well. The structure includes that a valve plate is provided with a plurality of valve pins, the upper end of each valve pin is provided with a seal ring and is arranged in a valve groove, and the valve pins are capable of moving up and down along with the valve plates in the valve grooves when the valves move. The valve plate is tightly pressed on a valve seat through a seal compressed spring, and a through hole is formed in the valve seat. The total area of the through hole which is formed in the valve seat is equal to the total area of a valve pin hole. When no liquid is drained, the force on the valve seat is equal to the pressure applied by the seal compressed spring. When liquid is drained and when the upward pushing force on the valve plate exceeds the downward pressure on the valve plate, the check valve is opened, and well liquid is drained from the down-mine to the g