Sum-frequency　generation　(SFG)　vibrational　spectroscopy　is　a　second-order　nonlinear　optical　spectroscopy　technique.　Owing　to　its　interfacial　selectivity,　SFG　vibrational　spectroscopy　can　provide　interfacial　molecular　information,　such　as　molecular　orientations　and　order,　which　can　be　obtained　directly,　or　molecular　density,　which　can　be　acquired　indirectly.　Interfacial　molecular　behaviors　are　considered　the　basic　factors　for　determining　the　tribological　properties　of　surfaces.　Therefore,　owing　to　its　ability　to　detect　the　molecular　behavior　in　buried　interfaces　in　situ　and　in　real　time,　SFG　vibrational　spectroscopy　has　become　one　of　the　most　appealing　technologies　for　characterizing　mechanisms　at　friction　interfaces.　This　paper　briefly　introduces　the　development　of　SFG　vibrational　spectroscopy　and　the　essential　theoretical　background,　focusing　on　its　application　in　friction　and　lubrication　interfaces,　including　film-based,　complex　oil-based,　and　water-based　lubricating　systems.　Real-time　detection　using　SFG　promotes　the　nondestructive　investigation　of　molecular　structures　of　friction　interfaces　in　situ　with　submonolayer　interface　sensitivity,　enabling　the　investigation　of　friction　mechanisms.　This　review　provides　guidance　on　using　SFG　to　conduct　friction　analysis,　thereby　widening　the　applicability　of　SFG　vibrational　spectroscopy.