An adjustable and controllable flexible bendable biological lumbar vertebrae structure system for a four-foot robot belongs to a novel biological lumbar vertebrae structure system for the four-foot robot. Aiming at the phenomenon that the animal lumbar vertebrae function of the conventional robot is always neglected or the introduced animal lumbar vertebrae function is not fully achieved, the invention provides the adjustable and controllable flexible bendable biological lumbar vertebrae structure system for the four-foot robot, which fully imitates the structure and functions of the lumbar vertebrae of an acinonyx jubatus, can achieve functions of the four-foot robot, including explosive jump, smooth furling and unfurling of four feet, specific body posture immovability and the like via connection of properly bent elastic steel plates and quick movement and coordination control of a dual-direction inverse spiral quick regulation mechanism; and in addition, the action of energy absorption and shock reduction of the elastic steel plate is fully utilized; a plurality of connection threaded holes in the joints of the elastic steel plate can achieve control of positions of a front part and a rear part of the lumbar vertebrae, as a result, the adjustment and control of the size of the total length of the robot are enhanced.