The electrohydraulic hybrid steering system (EHHS) was applied to the heavy vehicle, which had the steering angle tracking problem when working in the unmanned mode. In order to solve this problem and improve angle tracking performance, a complete nonlinear EHHS dynamic model was established, considering the parameter uncertainty and external disturbance. Based on the model, an adaptive doubleclosedloop angle tracking control strategy was proposed, in the external control loop, the parameter adaption law was designed to solve the parameter perturbation problem, and the improved sliding mode control strategy was used to calculate the desired steering torque; in the internal control loop, the PI controller was used to control the current of the steering motor to track the desired steering torque produced by the external control loop, and completed the steering operation finally. The EHHS model and proposed control strategy were built and simulated in Matlab/Simulink to compare the control effect of the new controller and the general linear controller. The results of the simulation verified that the control strategy proposed can effectively shorten the angle tracking response time of the EHHS system, which would remarkably reduce the steering angle tracking error under various operating conditions and ensured the tracking accuracy was not influenced when the system parameter was perturbed, and effectively improved the steering angle tracking performance of EHHS system in unmanned mode.