Gallium-based liquid metal (GLM), which combines superior lubricity, wide temperature range stability, and vacuum environment adaptability, is an emerging space lubricant. This study explores the frictional and wear characteristics of GLM for Cu/Al tribo-pairs under coupled vacuum-high temperature conditions. Under GLM lubrication, the friction coefficient and wear rate are decreased by approximately 0.5 ∼ 1.1 times and 7.1 ∼ 15.7 times respectively compared to dry friction. The excellent lubricating performance of GLM stems from the in-situ formation of a complete and continuous Ga-Al metallic friction film on the Cu alloy surface. The boundary lubrication effect generated by this friction film, in synergy with the fluid lubrication inherent to the liquid metal itself, effectively prevents direct contact between the frictional interfaces. However, high temperatures induce thermal softening of materials and intensify interfacial reactions, driving the further development of plastic deformation and corrosive wear of tribo-pairs, thereby leading to increased friction and wear.