During the operation of accumulatortype hydraulic pumping unit based on secondary regulation technology, the suspension speed changes, the input or output power of variable pump/motor connected with load hydraulic cylinder and the output or input power of variable pump/motor connected with accumulator mismatch, resulting in motor power instability and even reverse operation. The dynamic power compensation principle based on feedforward control was proposed on the basis of the energy conversion relationship of the system. The simulation results show that the fluctuation of motor power decreases in two cycles, and the power supply to the power grid will not reverse in the process of suspension speed change. The variable displacement pump/motor connected with accumulator can be adjusted adaptively. When the suspension load of pumping unit was disturbed by random uncertainties, the reducedorder observer was used to reconstruct the load disturbance, and the influence of the load disturbance on the output of the system was eliminated by feedforward control. The simulation results show that the control reduces the overshoot of the sucker rod speed and improves the steadystate accuracy of the speed. The variable displacement pump/motor connected with the load hydraulic cylinder can be adjusted adaptively.