Environmental Impact Assessment(EIA) is developing as a tool for environmentally sound and sustainable development in Korea. For more effective implementation of it, we try to apply Environmental Information System (EIS) to EIA process. EIS is composed of geographic and attribute data related to environment and Geographic Information System(GIS), and it will be applied to scoping, prediction, and alternative assessment, etc. in EIA. This study focuses on application of geographic data using GIS in suitability analysis of alternative assessment. We use TIN, buffering, and overlaying in GIS functions.