In order to satisfy the tractor speed and power requirements under various operation conditions, the control and interaction system of tractor hydro-mechanical CVT was studied. The principle of power split mechanism and infinite speed variation of a new kind of hydro-mechanical CVT were introduced. And the control method of infinite speed variation and load adaptive adjustment were analyzed. On the one hand, a point-to-point control method was studied through dividing the range of speed ratio into 96 work points, and building the mapping between work point and the actuators such as the exciting voltage of pump, the electromagnetic valve for pump flow direction control, and the electromagnetic valve for clutch control, the controller described the mapping as a control table to realize the infinite speed variation and power shift. On the other hand, based on the target of engine power control, an automatic speed ratio control strategy was proposed to follow the change of load and the corresponding fuzzy control table was acquired. The interaction system and control unit of tractor hydromechanical CVT were designed for further research. Finally, based on the presented control system, some key experiments such as tractor acceleration and load adaptive speed ratio adjustment were made. The test of acceleration showed that there was a stationary process for speed ratio adjustment with algorithm of point-to-point control under different work conditions due to the open loop control method. The test of load adaptive speed ratio adjustment showed that the speed ratio was quickly changed under different load levels to maintain the constant of engine power because of the closed loop control method. Results showed that the designed control system was reliable and the proposed algorithm was correct.