In Shanghai offshore area, coastline and underwater topography data in 1983, 1997, 2002 and 2009, are analyzed and compared respectively for recovering the topography evolution history and exploring their driving mechanisms. The results show that the Shanghai coastal area was generally in a silting-up state since 1983, but the evolutional patterns and dominant mechanisms changed remarkably in different stages. This paper proposed that, with the operation of South-North Water Diversion project, the local coastal erosion tends to increase in the following years, and close attention should be paid to its possible adverse effects.