A high-precision transmission mechanism of a machine tool is characterized by comprising a driving device, a shaft coupler, a driving wheel, a main shaft, a key, a retainer ring, a pin, a driven wheel, a shaft and an equalizing slot, wherein the driving device is in transmission connection with the main shaft through the shaft coupler; the driving wheel is mounted and connected to the main shaft through the key and the retainer ring; the driving wheel is externally tangent with the driven wheel; the shaft is arranged inside the driven wheel through the key and the retainer ring; the pin and the equalizing slot are formed in the driven wheel; the driving device adopts a motor. The high-precision transmission mechanism of the machine tool has the advantages of simple structure, small occupied space, stable transmission, low gear wear, low energy consumption of the machine tool, long service life, reduction in production halting frequency, convenience in mounting and dismounting, reduction in machining difficulty and reduction in machining production cost.