The present work has its technical background in the field of Diesel injection systems of combustion engines and compares the effects of two kinds of remedies (re-meshing technique and linear interpolation technique) on mesh deformation. Mathematical formulation of moving grids has been proposed to guide the change of cell volume before. In this study, CFD (Computational Fluid Dynamics) analysis was mainly involved to study the internal nozzle behaviours and spray characteristics. An external library concept was introduced to couple the internal nozzle injection process with spray formation. In addition, all dynamic simulations were performed under a double-axis system. The comparison between simulation and experimental results shows that the integration of the traditional mesh deformation technique with the re-meshing or linear interpolation technique can repair mesh deformation and further contribute to better simulation results. In particular, the introduction of linear interpolation technique results in better effects when the needle moves from some opened state. Moreover, this study solves the technically locked simulation problem, namely that needle opens from the closed state in nozzle-flow simulation, by applying the re-meshing technique. As a result, the completed numerical model can be designed and some important flow characteristics have been observed during needle opening and closing processes.