The invention provides a reducer and a high-speed shaft bearing lubricating structure of the reducer. The high-speed shaft bearing lubricating structure of the reducer comprises a box body, a bearing, an oil thrower, an end cover and an oil baffle disc. The oil baffle disc is fixedly connected with the end cover or the box body, and an annular gap communicated with an oil hole of the box body is formed between the oil baffle disc and the bearing. The oil baffle disc is fixedly connected with the end cover or the box body, and circumferential or axial positioning of the oil baffle disc can be achieved; an interval is reserved between the oil baffle disc and the bearing and forms the annular gap to serve as an oil returning hole; when the oil baffle disc is mounted, the fixing position on the oil baffle disc and the mounting position on the end cover or box body only need to be aligned, positions of other holes do not need to be considered, and a gap between the end cover and the oil baffle disc does not need to be considered, so that the mounting difficulty is reduced, and the assembling efficiency is improved. In addition, circumferentially-positioned pin holes and the oil returning hole for heat exchange do not need to be machined in the oil baffle disc, the structure is relatively simple, machining is facilitated, and the machining difficulty of the oil baffle disc is reduced.