Abstract: The effects of pulsing parameters including pulse duration, frequency and energy of single pulse on heat conduction weld shape parameters, which are expressed by penetration depth, bead width and depth-to-width ratio during pulsed Nd:YAG laser welding of 2 mm thick LF3 sheets under constant average power and welding speed, are studied. "Effective Peak Power Density" is introduced with the consideration of discontinuous action of pulsed laser welding to comprehensively study the effects of welding speed, frequency, pulse duration and spot size on weld shape parameters.The specific layered microstructure of pulsing laser weld is also studied. The results show that the weld shape parameters are affected both by pulse duration and peak power density.The welds under pulsed laser welding present layered microstructure, and the number of layers increases as frequency increases.