In recent decades, morphological changes in Cua Lo, Quang Nam Province, Vietnam are taking place very seriously and adversely affect regional economic development activities. Based on satellite images analysis, the previous research has been carried out that the main causes o f the elongation o f up-drift sand spit which leads to the severe erosion o f the south bank o f the river mouth. However, a detailed understanding o f wave - current interactions and their relation into the sand spit morphological changes in Cua Lo is still unclear. In this study, the numerical simulation (Delft 3D) is utilized to simulate the hydrodynamic regimes in response to sand spit elongation and their influence on the morphology- o f the inlets. Ás a result, the relationship between the hydrodynamic regime and morphological change process in Cua Lo Inlet have been clarified.