The invention discloses an automatic leveling system and method for a six-point support bridging platform; six supporting legs are respectively provided with a pressure sensor and respectively connected with a hydraulic device; each hydraulic device is connected with the pressure sensor and an electro-hydraulic servo valve; and a controller is respectively connected with an alarm, a double-shaft tilt sensor, each pressure sensor and each electro-hydraulic servo valve. Coarse adjustment is performed firstly, and then fine adjustment is performed; the coarse adjustment comprises the steps of: inputting a sensed pressure signal of each supporting leg to the controller by the corresponding pressure sensor on the supporting leg, if the pressure value of the supporting leg is less than a preset value in the controller, controlling the alarm to emit an alarm by the controller, or else, performing the fine adjustment; and the fine adjustment comprises the steps of: keeping two middle auxiliary supporting legs still, adjusting two forward supporting legs and two backward supporting legs, keeping the highest supporting leg still, firstly leveling an X direction, and then leveling a Y direction. The automatic leveling system and method for the six-point support bridging platform can ensure that the platform can be automatically leveled in an outdoor severe environment, the good levelingprecision and speed can be obtained, and strong environmental applicability and safety are provided.