As a new navigation technology on civil aircrafts the Head-Up Display (HUD) plays an important role in such aspects as improving civil aviation transportation safety increasing flight punctuality rate and reducing operation cost.It is finding wider application in civil aviation transportation currently.The paper describes the working principles characteristics and functions of the HUD and presents an analysis to the benefits of using HUD on civil aircrafts.In addition the composition work principles and roles on civil aircrafts of Head-up Flight Guidance System (HFGS) and Enhanced Flight Vision System (EFVS) which are developed from HUD are also analyzed.