Power-off protection device of hydraulic servo compensation system of spindle system of floor type boring and milling machine

The utility model discloses a power-off protection device of a hydraulic servo compensation system of a spindle system of a floor type boring and milling machine. The power-off protection device comprises an electric control one-way valve arranged between an oil tank and an electric-hydraulic proportional servo valve. When the floor type boring and milling machine is in a power-off use state, the oil tank is communicated with the electric-hydraulic proportional servo valve through the electric control one-way valve in a one-way mode. When the machine tool shuts down or is powered off suddenly, oil in a balance hydraulic cylinder cannot return to the oil tank, pressure adjusted by the electric-hydraulic proportional servo valve is kept all the time due to the electric control one-way valve, a spindle case is kept at the balance position adjusted before power-off, the damage to the machine tool because of spindle case unbalance caused by sudden shutdown or power-off is avoided, the machine tool is protected, and the compensation data of the machine tool before shutdown can be completely stored.