The invention relates to a power-off protection method of a spindle hydrostatic guideway. The power-off protection method of the spindle hydrostatic guideway comprises a power supply device, a power supply detecting device, speed adjusting devices, a controller, a DC/CD working power supply device, a spindle driving motor, a hydrostatic oil pump driving motor and the like. When a numerical control machine tool is normally supplied with power, spindle driving, feeding, hydrostatic oil pump driving and the like normally operate according to an order of the controller correspondingly. When external power supply is abnormally interrupted, the working procedures and steps of the power-off protection method of the spindle hydrostatic guideway are that an external power supply is detected, specifically, the external power supply circularly operates to monitor an external power supply signal and sends the detected signal to the controller; when the external power supply is interrupted, the external power supply is subjected to protective control; whether a hydrostatic spindle operates or not is judged; if the hydrostatic spindle operates, mechanical kinetic energy is converted into electric energy, and the electric energy is stored into the power supply device to supply power to the hydrostatic oil pump driving motor; and if the hydrostatic spindle stops operating, spindle hydrostatic guideway protecting work is completed. The power-off protection method of the spindle hydrostatic guideway has the advantages that the structure principle is simple, cost is low, the resources are recycled, free of pollution is achieved, and reliability and safety are high.