The invention relates to the field of fine flattening of lands, in particular to a GNSS (global navigation satellite system) based intelligent flat shovel control system and method and a flat shovel device applying the control system. The system comprises a GNSS positioning unit and a height adjusting unit, wherein the GNSS positioning unit comprises a GNSS base station and a GNSS moving station. The GNSS base station is used for receiving GNSS signals and calculating and transmitting differential signals. The GNSS moving station is used for receiving the differential signals from the GNSS base station and calculating and transmitting spatial information. The height adjusting unit comprises a controller, an electro-hydraulic directional control valve and a hydraulic cylinder. The controller is used for receiving the spatial information output by the GNSS moving station and transmitting action commands to the electro-hydraulic directional control valve connected with the hydraulic cylinder. By the GNSS based intelligent flat shovel control system and method, the problems about limited operation range, low operation efficiency, failure in accurate operation on slopes, large error in large-range operation, poor environmental adaptability and the like of laser control on the flat shovel device are solved.