The invention relates to a hydrostatic displacement feedback quick on-off mechanism. The hydrostatic displacement feedback quick on-off mechanism senses a steering angle through an oil cylinder piston rod so as to achieve communication of two hydrostatic cavities of a hydrostatic system through a follow-up control valve during small-angle steering of a front steering axle group, and transmits a non-hydrostatic steering signal to a rear steering axle group to achieve locking and non-steering of the rear steering axle group. In addition, when an oil cylinder is located at the middle position, automatic centering and oil supplementation of the hydrostatic system is achieved. Actual running of multiple cars proves that the steering performance is good, the problems including reliable transmission of grouping steering hydrostatic signals of large multiple-axle launching vehicles, small-angle steering stability, zero offset and oil supplementation of the hydrostatic system and the like are solved, and the steering stability, safety and reliability are effectively improved.