Abstract: Aiming at the problems of poor adjustment accuracy and slow adjustment speed of the existing driving speed control system of mechanical shift tractor, an automatic driving speed control system is developed based on the power shift tractor New Holland T1404. The control system includes tractor working condition information acquisition, communication, transmission gear control, throttle control and other modules. The control methods of tractor gear calculation and throttle adjustment are proposed to automatically adjust the engine and gearbox, so as to realize the accurate control of the working speed of power shift tractor. In order to test the operation effect of the control system, experiments were carried out under no-load conditions on cement ground and field ground. The test results show that under the two working conditions, the maximum speed regulation error of the control system is 0.15km/h, the maximum relative error is 3.0%, and the maximum regulation time is 4.4s, which can meet the production requirements of the automatic speed control process of the tractor.