At present, one of the challenges which Ca Mau province is facing is the coastal erosion. Each year, its coastal line has been averagely eroded by 5 km within its total length of 254 km; therefore, Ca Mau province has yearly lost by 927 ha of land. Especially, the erosion of the western coastal region of Ca Mau is extremely worrying. The analysis results have shown that the western coastal line has been eroded most in the right bank region of Ong Doc river and then Huong Mai estuary. In the other hand, the deposit region has been the cape of Ca Mau. In general, the coastal and estuarial erosion phenomenon has occurred in almost the Ca Mau province due to such reasons as: the characteristic of coastal line topography, geologic structure, wave, wind, tide, flow in river - sea and human, etc. The reasons have affected hugely the stability of provincial habitant, and social and economic situation. This paper introduces the result of investigating the change of coastal line, topography, and geologic structure in the western coast of Ca Mau to contribute to the evaluation of erosion reasons and then proposing the solutions to limit the negative effects.