Abstract: This paper focuses on theoretical connections between dynamics of variable mass systems and Reynolds transport theorem in continuum mechanics. Reynolds transport theorem is of fundamental importance as it is the general theoretical foundation for transport phenomenon of mass/momentum/energy in continuum mechanics (e.g., fluid mechanics). Based upon a thorough comparative study, we will show that: dynamics of variable mass systems in classical mechanics, although developed for general discrete particle systems, and transport laws in continuum mechanics essentially belong to the same theoretical framework and encompass similar analysis tools. If introducing continuous/smooth assumption into particle systems, conclusions in dynamics of variable mass systems can be extended to transport laws in continuum mechanics (including mass/momentum/energy).