Based on the extended application of COMSOL, a novel type of dual heat source model for pulsed laser-GTA hybrid welding was established. This model successfully solved the inaccuracy problem of simulation caused by energy superposition effect between laser and arc due to their different physical characteristics. Numerical simulation for pulsed laser-GTA hybrid welding of Magnesium alloy process was conducted, and the simulation results show good agreements with the measured thermal cycle curve and the shape of weld beads. Effects of pulse laser parameters (laser excited current, pulse duration and pulse frequency) on the temperature field and weld-pool were investigated. The experiment and simulation results show that when the laser pulse energy keeps constant, welding efficiency of the hybrid heat source is increased by increasing laser current and decreasing pulse duration due to the increased ratio of the weld bead depth to width. At large laser currents, severe spattering tends to occur. For a better welding process, the laser current should be controlled in the range of 150A-175A, the pulse duration should be greater than 1ms, and the pulse frequency should be equal to or slightly greater than 20Hz.