Abstract: Variations of the nearshore seabed erosion and accretion directly reflect the stability of the geomorpholo gical status of the sea area, which will furtherly affect the sediment migration and the sustainable utilization of waterway resources. In this study, Cangnan sea charts in different periods are selected to diagnose the process of multiscale seabed erosion and accretion in the nearshore zone by ArcGIS platform. The study will provide theoretical guidance for the planning and evaluation of harbor construction along the coast. The results show that the process of seabed erosion and accretion can be divided into four stages. A significant erosion from 1931 to 1970 is that the net deposition over seabed was 169.47×10⁶m³ and the average annual deposition thickness was 5.18 cm. The net deposition over seabed from 1971 to 2005 was 12.24×10⁶m³ and the average annual deposition thickness was 0.41 cm. From 2006 to 2009 the net erosion over seabed was 14.7×10⁶m³ and the average annual erosion thickness was 3.60 cm. Moreover, the erosion information from 2010 to 2017 can be discerned by the net erosion of 10.17×10⁶m³ and the average annual erosion thickness of 1.33 cm over seabed. moreover, all of 10 m isobaths migrated seaward from 1931 to 1970 and part of 10 m isobaths migrated seaward from 1971 to 2005 while 5 m and 10 m isobaths from 1971 to 2017 generally moved landward. Accordingly, it is expected that the study area will exhibit a weak erosion in the future. That the frequent storm surges leads to the regular instability of the seabed and the sharp decrease of suspended sediment discharge from the Yangtze River leads to the insufficient sediment supply may be responsible for the present erosion in the study area.