Abstract: A rod pumping unit used in the oil field, which has high efficiency and saves power, characterized in that: for the connection of the 2.omega. crank and the main crank in the 2.omega. crank balance device there is provided a differential phase adjusting mechanism, for the walking beam balance there is provided beam balance mass lowering device having positioning mechanism or self positioning mechansim, these devices can be adjusted manually in non-stopped status or by computer. The advantages of the pumping unit of the present invention are that the torque fluctuation of the speed reducer is small, the negative work of the power machine is eliminated and the power consumption and the total weight of the machine are decreased greatly. The present invention may save power and material to 50% as compared with the conventional beam pumping unit.