Abstract: According to available formation and field survey it is confirmed that largescale land subsidence occurred along the present Puqian port during the Qiongzhou earthquake of 1605,leading to changing the Sanjiangshui River course-generation of the tributary (the Dongzhai River).After the earthquake in point,large-scale land subsidence was continuing in a low speed and eventually the present Dongzhai Port that streches into the inland for the largest distance has so far been formed.