A　computational　analysis　is　achieved　during　laser　deep　penetration　welding.　Multiple　reflection　and　absorption　are　implemented　simultaneously　with　the　ray　tracing　technique　in　the　keyhole.　With　all　the　governing　equations　including　continuity,　momentum　and　energy　equation,　the　VOF　method　is　adopted　to　trace　the　free　surface　of　the　molten　pool.　Temperature　field　is　achieved　by　numerical　simulation.　The　laser　keyhole　welding　experiments　on　304　stainless　steel　sheet　showed　that　the　computational　results　agree　well　with　experimental　results.