Keyhole　effect　is　one　of　the　characteristics　during　deep　penetration　laser　welding.　Laser　keyhole　results　in　obvious　improvement　of　the　coupling　efficiency　of　laser　power　in　the　metal　sheet.　The　laser　energy　attenuation　along　the　thickness　of　the　sheet　occurs　due　to　the　inverse　bremsstrahlung　absorption　inside　the　keyhole.　On　the　other　hand,　the　keyhole　plasma　plays　welding　heat　source　role　in　transferring　laser　energy　to　melt　pool.　As　a　result,　a　combination　of　a　rotary　volumetric　heat　source　with　a　double　ellipsoid　volumetric　heat　source　was　proposed,　and　the　governing　equations　consisting　of　mass　conservation,　momentum　conservation　and　energy　conservation　for　the　incompressible　fluid　flow　and　heat　transfer　are　solved　using　SIMPLE　algorithm　based　on　control　volume　method.　Influence　of　weld　process　parameters　on　the　keyhole　dimensions　was　simulated.　In　addition,　validation　experiments　were　carried　out　in　order　to　compare　weld　shape　and　its　size.