Aimed at the characteristics of the ankle joint like quick-change-of-angle and multi-degree-of-freedom, we propose an active booster exoskeleton based on a multi-branch spatial linkage mechanism to assist the movement of ankle joint. The exoskeleton is driven by motor combined with a spatial linkage mechanism to achieve the active dorsiflexion / plantar flexion and adduction / abduction motion of the ankle joint for the purpose of locomotion assistance. The corresponding aim is to improve the coordination of ankle exoskeleton movement following and reduce the restricted freedom of movement on the wearer. Furthermore, gait recognition based on foot force measurement system and hierarchical control strategy using a motor state machine for ankle-assisted exoskeletons have been studied. The ankle joint was tested and assisted in the evaluation. The test results show that the effective power range of the ankle exoskeleton (plantar flexion 30° ~ dorsiflexion 20°, adduction 35° ~ abduction 15°) can meet the needs of normal walking with the good motion following (Angle error ≤2°) for the exoskeleton and the significantly attenuated lower leg EMG of the subjects by 28. 91% , which can provide effective power.