Static pressure balancing device of transmission case

The invention discloses a static pressure balancing device of a transmission case, which is used for improving internal and external pressure imbalance of the transmission case (13) when a liquid pressure medium works. The static pressure balancing device comprises a gas pressure balancing pipe (11) which is communicated with an inner cavity (131) of the transmission case (13) and a gas conveying device (12) which is communicated with the gas pressure balancing pipe (11); a downward exhaust port (111) is formed at the bottom end of the gas pressure balancing pipe (11); when only the residual gas is overflowed form the exhaust port (111) and external liquid can not immerse into the gas pressure balancing pipe (11) by maintaining through the control of flow rate and pressure of gas sent by the gas conveying device (12) and sent into the gas pressure balancing pipe (11), the gas pressure in the gas pressure balancing pipe (11) and the fluid pressure at the exhaust port (111) are balanced; and when the installation height of the exhaust port (111) is equivalent to that of the transmission case (13), the internal pressure of the transmission case (13) is basically equivalent to the external pressure of that.