Tien Chau estuary, Ky Lo river is in the south of Xuan Dai bay, An Ninh Dong commune, Tuy An district, Phu Yen province. In recent years, Tien Chau fishing port have been heavily deposited, waterway for boats are difficult. Several numbers of ships are tilted and sunk when entering the docking port, directly affecting the economic development of the province. In order to effectively dredge sand at the river mouth as well as serve the design of future plans at the river mouth, the study of the history of the river mouth is very necessary. The paper applies remote sensing technology to study the morphology of the estuary area over a long period, thereby finding out the morphological fluctuation trends in Tien Chau river mouth's revolution. The study results show that the estuary area is filled mainly by the change of the northern coastline of the mouth. In which, the length of the river mouth fluctuates quite stably in the range of 50-150 m. The strip of north bank of estuaries tends to curl and concave inland.