Hydraulic systems remain the preferred actuation method for heavy-duty robotic arms under heavy-load and high-impact working conditions, owing to their high power density and excellent shock resistance. However, significant throttling losses at valve orifices and the dissipation of gravitational potential energy have long hindered energy efficiency improvements. To address these challenges, this study proposes a novel hydraulic–pneumatic energy storage system incorporating chamber-independent pump–valve coordinated control. In the proposed design, the driving chambers of a three-chamber hydraulic cylinder are independently metered and integrated with a coordinated pump–valve control strategy, which reduces throttling losses while enhancing motion controllability. The energy storage chamber of the three-chamber hydraulic cylinder is directly connected to a hydraulic accumulator to balance the gravitational load of the working device and overcome inertial forces, enabling efficient recovery and utilization of gravitational potential energy. Experimental results demonstrate that, based on the three-chamber hydraulic cylinder, the throttling losses of the proposed system are reduced by approximately 70%, and the overall energy consumption is reduced by about 30% compared with the load-sensing system.