A constant power control method based on speed feedforward PI control is proposed to address the demands of rapid erection and heavy loads in a three-hinge point erecting system. A variable speed, closed-loop pump-controlled electro-hydraulic servo system has been designed, which includes a servo motor, a quantitative piston pump, and an asymmetric multi-stage hydraulic cylinder. By considering the dynamics of the erecting system and the pressure and flow dynamics of the hydraulic system, a constant power control strategy has been employed to plan the erecting angle, motor speed, and system power. This approach integrates speed feedforward and position feedback to create a speed feedforward PI control. A heavy-duty erecting test platform based on the pump-controlled electro-hydraulic servo system has been constructed to verify the effectiveness of the proposed control strategy. Rapid erecting tests indicate that the new control method achieves a tracking performance that is 60% better than traditional PID control, while also demonstrating excellent stability.