IN　Fe-S　system,　the　content　of　the　surface-active　element　sulfur　increases　weld　penetration,　but　the　amount　of　sulfur　has　been　greatly　reduced　with　improved　steel-making　practice.　It　is　important　for　us　to　get　the　optimum　sulfur　content　under　specific　welding　conditions　and　improve　the　quality　and　the　reliability　of　the　weldment.　The　sulfur　content　affecting　flow　patterns　and　weld　penetration　at　home　and　abroad　for　recent　20　years　were　summarized.　Sulfur　can　significantly　influence　the　shape　and　size　of　the　weld　and　final　weld　metal　solidification　structure　by　altering　flow　patterns.　The　surface　tension　coefficient　is　a　function　of　both　temperature　and　composition.　It　is　shown　that　the　weld　penetration　and　the　aspect　ratio　are　not　only　determined　by　the　level　of　the　surface-active　element,　but　also　the　temperature　distribution　on　the　weld　pool　surface.　The　sulfur　content　is　not　the　unique　factor　for　obtaining　the　optimum　aspect　ration　of　the　weld　pool.　The　current,　the　speed　of　moving　arc,　the　power　and　the　power　density　are　also　important　factors　in　controlling　the　temporal　evolution　of　weld　pool　geometry.