Underwater　hyperbaric　dry　gas　metal　arc　welding　(GMAW)　welding　technology　is　one　of　the　key　technologies　for　the　maintenance　of　underwater　equipment,　such　as　shipping,　ocean　platform,　seabed　pipeline.　To　get　high　quality　and　high　efficiency　underwater　welding　technology　parameters,　the　effect　of　hyperbaric　ambient　on　GMAW　is　of　important　practical　significance.　The　characteristics　of　the　weld　appearance　and　the　GMAW　process　were　studied　at　ambient　pressure　from　0.1　MPa　to　1.0　MPa　by　using　a　high-speed　camera　and　a　Hannover　analyser.　The　causes　of　weld　spatter　and　the　characteristics　of　weld　appearance　were　analyzed.　The　experiment　shows　that　as　the　number　of　the　spatters　increase,　the　weld　joint　becomes　narrower　and　worsens　gradually　as　the　ambient　pressure　increases.　©,　2015,　Shanghai　Jiao　Tong　University.　All　right　reserved.