Abstract: A passive energy-storage exoskeleton for assisting elbow joint is provided, which includes an upper arm unit, a lower arm unit, and an elbow joint unit located therebetween, the upper arm unit is rotatably connected with the lower arm unit. The elbow joint unit includes an anti-gravity mechanism, a coil spring mechanism, and a lower-arm-unit self-locking mechanism. The anti-gravity mechanism generates an equilibrant moment to eliminate the influence of the weight of the arm of the user and the weight of the device on the elbow joint. The lower-arm-unit self-locking mechanism is configured for locking/releasing the lower arm unit at any specified angle of rotation. The coil spring mechanism is configured for capturing and storing kinetic energy generated by rotation and swing of the arm of the user and releasing the energy as required.