During coaxial powder laser coating, the interaction between powder and laser directly affects the forming accuracy and quality of cladding. It is impossible to directly obtain the melting behavior of powder in laser and analyze the heat absorption of powder by infrared camera. Therefore, the dynamic behavior of powder melting is collected by high-speed camera system and the dynamic analytical model of powder melting process is established accordingly. The influence of laser power on different melting stages and the temperature characteristics of powder entering the molten pool are simulated and analyzed.The results show that: (1) There are three typical melting characteristic stages of 'solid → solid-liquid two-phase → liquid ' in the dynamic melting behavior of powder collected by high-speed camera in laser. The dynamic behavior of powder melting can be analyzed by mathematical analytical model, and the thermal physical behavior of different stages has a dynamic analytical model of powder and laser thermal interaction. (2) The effects of laser power, off-focus value and the flow rate of the gas carrying the powder on the melting behavior of powder were analyzed. At the same time, the effects of different laser power on the duration of each characteristic stage were simulated and analyzed. The temperature distribution of powder particles reaching the substrate was simulated and predicted. It was found that when the laser power increased from 100 W to 1 500 W, the temperature of powder entering the molten pool changed nonlinearly, from 750 ℃ to 3 250 ℃.