A method to calculate the interaction time between metal powder and laser beam during laser direct forming with the metal powder conveyed by coaxial powder feeder is introduced in detailed. A finite element method (FEM) model based on ANSYS software is established to calculate the temperature of the metal powder while it crosses through the laser beam. Under different laser power condition, after interaction with laser beam, the temperature of the 316L stainless steel (SS) powder of different size is calculated. Thus the laser energy absorbed from laser beam by metal powders is calculated. After 316L SS powders have entered laser molten pool, the energy exchange between laser molten pool and 316L SS powders is also calculated. The calculated results show that all 316L SS powders are melted after they have crossed through the laser beam with power larger than 1000 W. It is to say that the 316L stainless steel powders are turned from solid into liquid before they reach the surface of laser molten pool. The calculated results also show that during laser direct forming, approximately 5% of laser energy is used to heat and melt metal powders and 95% of laser energy is used to form laser molten pool and to compensate the heat loss due to thermal conduction.