The invention relates to an intelligent adjusting device for mechanized farming depth in protected cultivation, which belongs to the field of agricultural machinery. One end of a linear displacement sensor is connected with the rear end of a tractor, and the other end of the linear displacement sensor is connected with a tillage implement. One end of an upper horizontal rocking bar, one end of a middle horizontal rocking bar, and one end of a lower horizontal rocking bar are hinged to the rear of the tractor. The other end of the middle horizontal rocking bar and the other end of the lower horizontal rocking bar are respectively hinged to the tillage implement. The other end of the upper horizontal rocking bar is hinged to one end of an upper diagonal brace and a lower diagonal brace, and the other end of the upper diagonal brace is hinged to the upper end of the tillage implement. The other end of the lower diagonal brace is hinged to the middle of the lower horizontal rocking bar. The middle of the upper horizontal rocking bar is hinged to the top end of a piston rod of a hydraulic cylinder, and the lower end of a block of the hydraulic cylinder is hinged to the tractor. A signal output end of the linear displacement sensor is connected with a controlled end of a control valve through an intelligent control circuit. The intelligent adjusting device is capable of automatically adjusting farming depth to meet the operation requirements, and is simple in structure, highly implementable and easy in popularization and application.