The finite volume method (FVM) for three-dimensional convection current in inert gas condensation processing was carried out to understand the nanoparticle trajectories and distribution of dynamic pressure and static temperature in operating vacuum chamber. We have demonstrated that the region of the highest pressure as well as the fastest gas current was located near the source. It was shown that the swirl movement of gas convection in the vacuum chamber was dominant, which could increase the nanoparticle's thermophoresis to the cold finger. The nanoparticle trajectories simulated by single gas transport showed the paths for good product efficiency, which circulate straight upward from the source and then downward along the cold finger.