The invention belongs to the field of variable-stiffness mechanisms, and discloses a variable-stiffness energy storage mechanism applied to ankle and foot artificial limbs. The variable-stiffness energy storage mechanism includes a calf plate, a fixed leg, a spring connecting end A, a tension spring, a guide wheel, a spring connecting end B, a connecting rod and a conveying belt; one end of the tension spring is fixedly mounted on the spring connection end A, and the other end of the tension spring is fixedly connected to the spring connection end B; the spring connection end B has a sliding boss; an arc sliding groove is formed in the calf plate; one end of the connecting rod is mounted on the sliding boss, and the other end of the connecting rod is mounted on the calf plate; one end of the conveying belt is mounted on the fixed leg, and the other end of the conveying belt is fixedly mounted on the sliding boss. The variable-stiffness energy storage mechanism can simulate achilles tendon-like joints, the small stiffness can be realized when a support phase is transformed into a swing phase, a hydraulic cylinder rod stretches out to do positive work; and the stiffness is increasednonlinearly when the swing phase is transformed into the support phase, energy is absorbed and stored, and shock absorption is achieved.