A pumping unit auxiliary balance device is used for balancing of an oil field beam-pumping unit. The pumping unit auxiliary balance device is characterized in that a flexible pipe is connected on the bottom of a balance water tank, the flexible pipe is communicated with the inner portion of the balance water tank, the other end of the flexible pipe is connected with an outlet pipeline of a water pump, a water inlet of the water pump is connected with an outlet of a ground water tank through a pipeline, an inlet of the ground water tank is connected with an outlet of an electric control valve through a pipeline, and an inlet of the electric control valve is connected with the other end of the flexible pipe through a pipeline. The pumping unit auxiliary balance device has the advantages that balance of a pumping unit does not need to be adjusted during machine halt, the total mass of the counterweight of the pumping unit can be automatically adjusted and changed along with the loading of a motor, the pumping unit can be kept in a good balancing state, and manual operation is of no need.