Aiming to enhance the comprehensive steering performance of a high-clearance self-propelled sprayer operating under complex and uneven field conditions, focusing on improving steering response speed, driving stability, minimizing turning radius, and mitigating tire sideslip-critical factors for efficient and damage-free crop protection operations, based on a hybrid control strategy that integrated proportional feed forward control with yaw rate feedback, a full hydraulic four-wheel steering system employing a fuzzy PID controller was proposed and developed. Co-simulation conducted in AMESim and Matab/Simulink demonstrated that the designed control system achieved precise coordination between front and rear wheels, with the maximum following error of the rear wheel angle relative to the front wheel command remaining within ±1.8°, fully satisfying the geometric constraints of Ackermann steering theory. To further validate the system's effectiveness, a physical prototype test platform was constructed. Random steering tests were performed at a representative working speed of 4 km/h in four-wheel steering mode. Notably, the implementation of the four-wheel seering mechanism reduced the vehicle's minimum turning radius from 7.9 m (in two-wheel steering mode) to 4. 8 m-a 39. 2% reduction-significantly enhancing maneuverability in narrow rows and headland turns, while simultaneously improving lateral stability and operational efficiency during fieldwork. These outcomes underscored the system's potential to facilitate the transition of agricultural machinery from conventional mechanical steering toward intelligent, adaptive, and high-performance autonomous operation.