Taiwan, an island nation, has an area of 36,000 square km and coastlines of about 1,600 km. Because the human activities, industrial production, and economic development have mostly taken place on the coastal plains, Taiwan is facing overpopulated and overdeveloped problems on the coastal areas. A project to establish a fully GIS-based system to manage coastlines is presented in this paper. Firstly, the project converts all maps associated with the coastlines to the digital form and integrates into a GIS system. Secondly, the system which contains a variety of functions of the image processing and spatial analysis is designed to measure the length of the coastlines from a series of SPOT satellite images and aerial photos. Consequently, the associated statistics of the coastline data is analyzed and presented to the related government organizations.