This article reported the macroscopic and microscopic study on the wear-out failure of bearings and, further explored the state-of-art lubricants in the rotating anode X-ray tube for medical devices from the view of vacuum lubrication. The techniques including Optical Microscope (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Electron Dispersive Spectrum (EDS) were adopted to characterize the worn morphology, chemical composition and lubricating medium over the bearings components. The results showed that the bearings in the rotating anode X-ray tube was made of SKH4 or M50 steel, while the lubricant materials were MoS2 and Pb-Cu alloy respectively. As compared with Pb-Cu alloy solid lubrication approach, MoS2 solid lubricant was prone to produce wear debris and dust phenomenon. It was found the main failure at the outer and inner raceway of the cold end of bearing resulted from abrasion, while predominant abrasive wear and fatigue symptoms occurred at the hot end of bearing. Moreover, electrical ablation and pitting corrosion were found at the localized regions of bearing components due to arc discharge at the contacting interface. The typical cause of the bearing failure in the rotating anode X-ray tube was attributed to wear, the developing trend of lubrication for the bearing components in the the rotating anode X-ray tube at present and in the coming long period of times was perceived.