Numerical simulation provides a way to improve our understandings of the heat transfer and fluid flow behaviors of the weld pool during laser keyhole welding. However, current numerical studies are only limited to serial simulations which running on a single CPU. In this study, a parallel numerical study of the heat transfer and fluid flow of the weld pool is presented. A mathematical model considering the effect of Marangoni force, buoyancy force, friction force of the mushy zone region and the effect of keyhole is presented. A combined keyhole volume and surface heat source model is also developed. The coupled transient heat transfer and Navier-stokes equations are solved with a high order accuracy parallel projection method. The simulation code is parallelized with the OpenMP language. It is shown that 200% speedup can be achieved on a shared memory quad-core CPU using the presented parallel simulation system. The simulation results agree well with the in-situ high speed CCD video imaging experiments and the literature results.