This paper presents an improved oil spill model, coupled with a current model based on a 2D finite-difference grid. The aim of this study is to make the models more accurate and faster than the old ones. The current model gives the velocity distribution on the surface of water body and in the case of transient analysis, the velocity distribution is computed at each computational time step. This velocity distribution will be taken as the input for the oil transport simulation model. The oil spill model computes and predicts the oil distribution and the spill size. There are two improvements in this research: moving boundary to get the more correct results and nested grid to help the models run fast. The computational results in the study area are agreement to experimental results and real data in Can Gio coastal zone. So they can be applied in reality.