The invention relates to an oiltight structure of a motor shaft tube, comprising a shaft tube, a bearing, a rotating shaft and a leakproof sheet. The shaft tube is provided with an inner hole which is provided with a large diameter part and a small diameter part; the large diameter part is arranged at one end of the inner hole, the other end of the inner hole is a closed blind hole; the bearing is arranged at the small diameter part and provided with a shaft hole in the center; the rotating shaft is articulated with the shaft hole of the bearing and provided with a reduced diameter part on the periphery surface; the leakproof sheet is fixedly arranged on the large diameter part and provided with a limit hole in the center; and the peritreme of the limit hole is embedded in the reduced diameter part of the rotating shaft. Accordingly, the invention can utilize the leakproof sheet to block the leakage path of lubricating oil and can prevent the rotating shaft from axially moving or loosening, thereby simplifying the spare parts of the motor.