Facing the environment problems, the improvement on the efﬁciency of the construction machinery is highly demanded, meanwhile, large energy wasted in hydraulic slewing systems, reaching the desired speed slowly and vibration in braking are widespread. In this paper, a closed-loop control swing system (CCSS) is proposed. In this system, bidirectional variable pump controls the change of oil flow by programmed software algorithm, instead of pilot actuated reversing valve, which signiﬁcantly improves the efficiency of hydraulic circuit. Based on the model structures, we develop a hydraulic swing prototype and verify the advantages of our design means of theoretical calculation and simulation. It verifies that CCSS and based on accumulator slewing system(BASS) can respectively save 875.5 KJ and 347.2 KJ more than OCSS with operational weight of 100 tons grasp steel machine, which can support theoretical basis for energy conservation and environmental protection to study the new type of engineering machinery.