Abstract: In order to analyze the lubrication characteristics of space silicon-hydrogen lubricating oil (SiCH) under boundary lubrication condition in vacuum, the nominal lubrication lifetime of lubricating oil under the contact stresses of 1.5, 1.75 and 2 GPa were tested by Spiral Orbit Tribometer (SOT). The reciprocating sliding friction coefficient of the lubricating oil was tested by SRV, and microscopic analysis was performed in combination with scanning electron microscope, X-ray energy spectrometer and X-ray photoelectron spectroscopy. The test results showed that the vacuum lubrication life of silicon-hydrocarbon lubricants was as long as 1 936 r/μg, and the sliding friction coefficient and the wear scar diameter were smaller than that of the 815Z perfluoropolyether lubricant. The infrared transmittance analysis of the lubricating oil before and after four ball test showed no significant variation on the transmittance of the lubricating oil in the 14~16.25 μm band. In the vacuum life verification test, the highest revolutions of two scanning motor with space silicon-hydrogen lubricating oil lubricated bearings was 6.04×10⁸ times. Lubricating oil tribological performance testing and life verification test results provided quantitative criteria for lubrication failure under boundary lubrication conditions, and also test basis for long-life lubrication design of space mechanisms under other similar operating conditions.