The utility model discloses a large-size high-speed precise direct-driven main shaft structure in an NC (Numerical Control) lathe, which relates to the technical field of mechanical engineering. The large-size high-speed precise direct-driven main shaft structure comprises a main shaft structure and a high-speed precise direct-driven NC lathe main shaft unit, wherein the main shaft structure is organically combined with a hydraulic dynamic-static pressure technology and an electric main shaft technology, and the high-speed precise direct-driven NC lathe main shaft unit is capable of realizing a large-size hydraulic hybrid bearing and is internally provided with an electric motor; the electric motor is arranged between a front hydrostatic bearing and a rear hydrostatic bearing. According to the large-size high-speed precise direct-driven main shaft structure disclosed by the utility model, the bearing span of a main shaft is enlarged, the main shaft is only in bearing with a circumferential rotating torque without a radial driving force as the external force action of an intermediate transmission link does not exist when the electric motor drives the main shaft to rotate, the high-speed running of the main shaft is more stable as no intermediate transmission impact exists, and the accuracy of processing parts is high; a sealing structure in circumferential and uniform distribution type and multi-point air outlet is uniform in pneumatic pressure and good in sealing effect; by adopting the large-size high-speed precise direct-driven main shaft structure, the rotating speed is high, the accuracy is high, the rigidity is large, the noise is low, the service life is long, the working stability is good, the working reliability is high, and the large-size high-speed precise direct-driven main shaft structure can be used for a precise processing machine and a main shaft of a high-speed and high-accuracy device.