During　modern　high-power　laser　manufacturing,　the　laser　beam-heat　energy　conversion　mainly　occurs　in　the　airliquid　interface　of　laser-induced　molten　pool　evaporation.　The　molten　pool　air-liquid　interface＇s　evolution　law　and　laser　energy　coupling　characteristics　were　performed　by　using　in-situ　optical　observations　and　numerical　simulation　in　this　study.　They　revealed　the　four　stages　of　this　evolution　process:　preheating,　expansion,　oscillation,　and　contraction.　In　the　expansion　stage　of　the　molten　pool,　the　molten　metal　will　flow　from　the　center　of　the　molten　pool　to　the　periphery　due　to　the　joint　action　of　surface　tension　and　laser-induced　evaporation　recoil　pressure,　and　the　air-liquid　interface　exhibits　a　middle　depression.　When　the　laser　is　turned　off,　the　evaporative　recoil　pressure　drop　causes　the　molten　pool＇s　oscillation,　which　amplitude　and　duration　positively　correlate　with　laser　power.　Due　to　the　effects　of　the　solid　state　and　the　air-liquid　interface　depression　after　melting,　the　absorptivity　first　drops　and　then　grows　with　the　increase　of　laser　power.　Eventually,　the　melting　efficiency　increases　with　laser　power.