The invention discloses a non-contact seal device for a high-speed shaft of a gear speed reducer. The non-contact seal device comprises the high-speed shaft, a sealing ring, a transparent cover, a static ring, a dynamic ring, an oil leakage groove, a bearing and a bearing sleeve. The bearing is arranged in the bearing sleeve, the transparent cover is fixedly connected to the outer end of the bearing sleeve and is provided with a lower edge stretching into the bearing sleeve, the static ring is arranged between the lower edge and the bearing in a pressing mode, the dynamic ring is fixedly connected to the high-speed shaft, and an axial labyrinth is formed by the static ring and the dynamic ring. The sealing ring is fixedly connected to the high-speed shaft, a ring groove is formed in the peripheral wall of the sealing ring, a radial labyrinth is formed by the sealing ring and an opening of the transparent cover, a cavity is formed between the radial labyrinth and the axial labyrinth, the axial oil leakage groove is formed in the lower edge and the inner wall of the bearing sleeve, and the oil leakage groove is communicated with the cavity and the inner portion of a box. The non-contact seal device is simple in mechanical structure, easy to machine and assemble, low in cost and capable of achieving the reliable sealing effect.