The Beacon Mounds play a important role in defence and communication extending from the period of the Three States to the period of Chosun. About the research of beacon mounds have focused on investigation in old literature. This research analyzed geographic factors such as altitude, cross section, distance and visible distance affect in selecting location of beacon mounds. And it was presumed how each beacon mound geographic characteristics was considered in selecting location of beacon mounds. As a result, it is presumed that communicating among beacon mounds and watching the coast were affected by geographic characteristics and selecting location of beacon mounds was considered by several geographic factors.