Abstract: The use of power curve data for adjusting balance for beam-pumping unit is a supplement to balance adjustment methods like current method, indicator diagram torque method, etc. With the popularity of power testing, the research on this method has received more and more attention. Analysis was performed of the relationship between the average balance power of crank counterbalance working on crack shaft and the position of crank counterbalance during up and down stroke; and a calculation model was established for balance adjusting amount by average power method for crank balance pumping unit, in conjunction with the relationship between the average motor output power variation and the average balance power variation of crank counterbalance working on the crank shaft, and based on the balance criterion of equal average motor output power during up and down strokes. This model was explained and further applied with the field operation, in order to further improve its practicability. The practical calculation results show that the model meets the requirement that the average motor output powers should be equal during up and down strokes, and the root-mean-square power of motor during the whole stroke was reduced from 9.444 4 kW to 8.423 7 kW, which helps energy-saving.