The energy absorbing behavior of stainless steel 304L during the pulsed Nd:YAG laser welding is investigated in this thesis. The equivalent absorptivity is estimated from the comparison of measured and finite element method (FEM) results simulated melting pool shape parameters, e.g. pool width, pool depth, cross-section area and total volume of the pool. To simulate the actual pulsed laser beam, the energy density of heating source is performed as a Guassian distribution in the transection of a circular laser beam. For evaluating the feasibility and the accuracy of the estimated equivalent absorptivity, the multi-pulsed Nd:YAG laser welding is simulated by using the estimated absorptivities. A good agreement between this simulated and measured melting pool shapes are found in the multi-pulsed laser welding. The equivalent absorptivity can be interpolated from different parameters of the molten pool. However, absorptivity curve fitted from the cross-section area and total volume of the melting pool provide a more stable value. Results also indicate that the absorptivity and the pulse energy are in inverse proportion. The thermal-elastic-plastic FEM model is employed to simulate the fusion and solidification process of the pulsed laser welding. A complicate residual stress distribution introduced from the shrinkage in the solidification process is also calculated and presented. The distribution of post-weld-deformation near the melting pool has also been studied in this thesis. This post-weld-deformation may be a key factor in high precision laser welding, e.g. laser packaging for the optoelectronic components. The absorptivity estimated in this thesis may be helpful to simulate the laser welding process accurately.