<p>Laser melt injection (LMI) is a key technology for fabricating high-performance particle-reinforced metal matrix composite coatings (MMCCs), with its core being the efficient coupling between ceramic particles and the molten pool. Laser-powder interaction under coaxial powder feeding directly determines coating quality. To reveal this interaction mechanism and its impact on coating quality, the work explores particle flight characteristics during powder feeding and their relationship with coating morphology via theoretical modeling and process experiments. Firstly, theoretical models for particle velocity and temperature in LMI powder feeding is established, and numerical calculations analyze the influences of particle diameter and carrier gas flow rate on particle velocity and temperature. Secondly, a high-speed camera is utilized for observing the velocity and temperature of particles during laser-powder interaction, verifying the theoretical models’ reliability. Finally, process experiments are conducted to explore the influences of particle diameter and carrier gas flow rate on coating morphology, and the relationship between powder stream characteristics and coating morphology is analyzed. Results show that reducing particle diameter or increasing carrier gas flow rate increases particle velocity, while particle temperature rises with the decrease in both. Low-velocity, high-temperature particles are prone to entering the molten pool, whereas high-velocity, low-temperature particles tend to rebound and spatter. A carrier gas flow rate of 6 L/min balances powder feeding stability and LMI success rate, serving as the optimized process parameter. This study establishes a quantitative relationship between laser-powder interaction and coating performance, providing theoretical and experimental support for fabricating MMCCs by LMI.</p>