Aiming at the problems of low power matching degree and poor fuel economy of the existing agricultural machinery speed regulation strategy, taking hydrostatic tractor as the platform, the cruise control system of the tractor was designed based on CAN bus. The system was composed of a tractor working condition acquisition module, a throttle control module, a variable pump displacement adjustment module, a work tool lifting control module, and a communication module. Devices of throttle adjustment and load adjustment were developed. Tractor working condition data was analyzed. Mathematical model of throttle opening, variable pump displacement and tractor speed was established. A strategy for cooperative control of engine speed and variable pump displacement was developed. The cooperative control strategy experiments on empty cement roads, empty farmland and flat working conditions were conducted; and the experiment of the fixed throttle control strategy, the throttle displacement coupling control strategy and the throttle displacement cooperative control strategy was carried out under the flat operation conditions. The test results showed that the absolute error of speed control of the cooperative control strategy was 0.005m/s, 0.007m/s and 0.012m/s under the three working conditions of cement pavement, field no-load and flat land operation; the cooperative control strategy reduced the engine speed under the premise of achieving the target speed. The control system can reduce fuel consumption while ensuring the accuracy of speed control.