The solidification behavior and the morphological evolution of 316L stainless steel during laser rapid forming (LRF) were investigated. It was found that, there shows a complete austenitic structure in the LRF sample within the processing parameters of this study, there was continued epitaxial growth of the g phase of the fine columnar dendrites from the substrate, with the <100> crystallographic orientation leaning to, even parallel to the deposition direction. There also exist a thin layer in which the dendrites grow along the laser scaning direction at the top of the LRF sample. Clad layer bandings were found in the samples; however, the continuity of the growth of the columnar dendrites was not upset. The growth morphology of primary dendrites can be predicted by the microstructure selection models based on the maximum interface temperature criterion. The formation of the clad layer bandings and the epitaxial growth characteristic during LRF are also explained by the criteria for planar interface instability and dendritic growth theory and the columnar to equiaxed transition model. There shows an reasonable agreement between the theoretic analysis and the experimental results.