Abstract: A downward offset barbell type walking beam compositively balance oil pump, in which at the rear end of the walking beam is mounted a downward offset barbell type balancing device consisting of a shoe plate, a cross shaft and balancing pieces, retains most of the structure of the conventional walking beam oil pump, and has a compact structure, a wide range of moment change, an advantage of saving electricity to a degree of more than 40 percent, and is safe and reliable for operation. The present invention can be applied to the renovation of variety of conventional walking beam oil pumps, used in oil fields, outphase crankshaft oil pumps and walking beam compositively balance oil pumps for the purpose of energy-saving or of promotion of the capacity for oil extraction of the above-mentioned oil pumps.