Abstract: Selective laser melting (SLM) is a key metal additive manufacturing process that has attracted increasing attention from both academia and industry. The dynamic changes of metal vapor and particle splashing during the SLM forming process of 316L powders were recorded through high-speed schlieren imaging experiments, and the influence of laser power on the metal vapor and splashed particles was analyzed. The results show that at high power levels, there is a greater amount of vapor jetting, the angle between the vapor motion direction and the laser scanning direction is bigger, the vapor motion speed is faster, and the distribution of splashed particles is more concentrated. Additionally, the vapor motion direction changes over time, and there are differences in the interval time for the vapor motion direction to change at different laser power levels. This provides some assistance for further understanding and recognizing the forming process of parts.