Facing severe environmental problems, to improve the efficiency of the hydraulic construction machinery is in great demand. The potential energy when the boom is lowering is dissipated as heat in hydraulic system. It is urgent to improve the maximum use of regeneration energy to reduce the fuel consumption. This paper first analyzes the proportion of regeneration energy for each actuator and studies the special working style of the boom energy regeneration system (ERS) in a 20-t HE. Then, types of the ERS are discussed. The research and development of the electric ERS technology and the hydraulic ERS technology based on construction machinery are reviewed. At last, the paper puts forwards the challenges and the future development of ERSs.