<p>Wedge cross rolling is an efficient and clean near-net forming technology for shaft parts. The development of large wedge cross rolling mills addresses the urgent demand for high-efficiency, environmentally friendly manufacturing of shafts used in high-speed rail, rail transit, aerospace, and related fields. To accommodate the large rolling forces required, a hydraulic press-down system is employed. To enhance synchronization control performance under partial load conditions, a mathematical model of the hydraulic press-down system is established. A synchronization control strategy that combines particle swarm optimization (PSO)-tuned proportional-integral-derivative (PID) control with cross-coupled synchronization is proposed. This method is evaluated against traditional PID and equivalent synchronization control strategies through model-based simulations. A dual-cylinder synchronization hydraulic test platform is developed based on the operating principle of the press-down system. Comparative experiments under different speeds and bias loading conditions are conducted on this platform. Results show that the combined PSO-optimized proportional-integral (PI) control and cross-coupling method significantly reduces synchronization errors between the two cylinders, thereby improving the system's synchronization accuracy. These findings confirm the feasibility and effectiveness of the proposed control method.</p>