Abstract: The degree of interaction between laser beam and powder particles decided the statue of the particles before entered the molten pool. In this paper, both the transient state image captured by shadowgraphy enhancement and image information processing were used to analysis the change characteristics of the whole powder stream and single particles after irradiated by laser from macro and micro perspectives. Characteristic parameters, including amount of high light particles, total area of high brightness area, the intensity of a single particles irradiated by laser were extracted to analysis the influence of the different parameters on the interaction between laser and powder particles. The results show that better regulation of the interaction between laser and particles can be achieved based on the reasonable match of main parameters. By increasing the laser energy density and the interaction time of laser and powder particles, the intensity of particles irradiated by laser is increased and the particles are more likely to enter the molten pool in liquid state.