The utility model discloses a power transmission mechanism of subsurface equipment. The power transmission mechanism is formed in a way that an equipment connecting shell is connected with a balanced short section; the balanced short section is connected in the cavity of an equipment sealing shell; and a supporting frame, a fixed piston and a sliding piston are connected and installed in sequence into one. The power transmission mechanism has simple structure and reasonable design, which is the reliable mechanism structure of the electric equipment for power transmission for balancing the external liquid pressure under the high pressure state in an oil-water well.