In this study, we used molecular dynamics (MD) simulations of the rupture process for a water film to define and determine the critical rupture time (CRT). This new approach could be an important method for authentically defining and determining the rupture point of a water film and associated phenomena. We were able to predict generically the CRT and the critical thickness of the water film. Then, we studied the effect of ions on the film rupture process. Our results showed that the addition of sodium chloride did not significantly affect the stability of the water film. Results from MD simulations, when compared with results from experimental measurements, can provide insight into the film rupture process.