The invention discloses a bionic mechanical leg imitating the motion function characteristic of an ostrich hind limb. The mechanical leg comprises a body, a hip joint motion mechanism, a knee joint motion mechanism and an ankle joint motion mechanism. The hip joint motion mechanism is composed of a motor and a crank-rocker mechanism, wherein the crank-rocker mechanism comprises a crank, a femur and a connecting rod. The knee joint motion mechanism comprises the femur, a first spring, a tibia, a metatarsus, a brake cable, a lower fibula, a second spring, an air cylinder and an upper fibula. The ankle joint motion mechanism comprises the metatarsus, a first apotelus bone, a second apotelus bone, a third apotelus bone, a third torsional spring, a second torsional spring and a first torsional spring. The ostrich hind limb capable of efficiently moving serves as the bionic prototype, through combination of testing on hind limb motion parameters during running of an ostrich and biological anatomic analysis, the mechanical leg imitating the ostrich hind limb is obtained through optimization design according to the tendon-bone and muscle-tendon interaction mechanism of the ostrich, and the mechanical leg is simple in structure, safe, reliable, low in vibration, and capable of efficiently saving energy.