Abstract: US space fence program is a large-scale ground-based radar system designed for future national security and civil application, which is presented so as to expand space target surveillance range, increase space target detection volume, boost space target detection accuracy and timeliness, especially detect small space targets. The program is intended to promote space situation awareness capability by means of tracking more and smaller targets as well as taking place of AFSSS being used by USAF since the year 1961. In the paper, purpose, composition, and function of space fence are introduced; key technologies, risk points, and management manner are analyzed.