The invention relates to a pre-detection active leveling system and leveling method for an agricultural vehicle working platform, and belongs to the technical field of vehicle platform leveling. The pre-detection active leveling system includes a platform, a cross universal joint, a base, a vehicle body, a suspension, wheels, a distance measuring sensor, a vehicle body tilt sensor, a platform tiltsensor, a platform tilt adjustment mechanism, a platform pitch adjustment mechanism and a central processor. In the walking operation process of an agricultural vehicle, the vehicle body tilt sensorperiodically measures the pitch angle and the roll angle of the vehicle body, and the distance measuring sensor periodically synchronous measures relative height information of the ground in front ofthe wheels, and calculates the pitch angle and the roll angle change amount of the vehicle body at the next moment, obtains the linear displacement adjustment amount of the platform tilt adjustment mechanism and the platform pitch adjustment mechanism under the condition of maintaining the platform level, the two adjustment mechanisms complete the predetermined linear displacement adjustment in the adjustment period, and the pre-detection active leveling of the agricultural vehicle working platform during the walking is achieved.