In order to solve the global optimization of energy consumption in the oilfield waterflooding system，the characterization approach of energy consumption in the oil reservoir system is established by using energy conservation law and characterization method of fluid energy. Physical meaning of each item for the characterization method is described. Based on the proposed model，the objective function is defined as the lowest energy consumption per ton of oil at certain stage. The characterization methods of energy consumption in the water injection system，oil reservoir system，lifting system and the oil reservoir development plan are considered as the constraint conditions. The oil production and water injection volume of single well in the water injection system are set as the decision variables. Then，global optimization model for energy con? sumption of oilfield waterflooding system is proposed. The global optimization method is applied to the plan optimization of a certain injection-production well group. Reservoir parameters may be obtained through numerical simulation. The optimal injection-production plan and formation pressure maintenance level are obtained，and the rationality of this method is verified.