With an area of 36,000 sq. km, Taiwan has about 58% of land is covered with forest. Seeking to a sustainable use of the forest land, Forestry Bureau is responsible for protection and conservation of the forest resources. One of its regular patrolling missions is to send forest rangers out to inspect the status of forest land and prevent any illegal activity. However, due to the limited manpower, the natural landslide and the illegal activity are hardly found in the remote mountain areas. A project to establish a forest change detection system is presented in this paper. The project regularly analyzes different period of SPOT-5 high spatial resolution images and provides the positions of the change spots for Forestry Bureau and the local forestry patrolmen. The practical exercise of the project shows that the satellite images certainly can be used to enhance the patrolling mission and to strengthen the forest protection.