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.