Space radiators are important components in spacecraft thermal control subsystem. The heat pipes can enhance the heat transfer capability of radiators. The heat pipe radiators are efficient and reliable space radiators. In this paper, the typical heat pipe radiator construction is introduced. The detailed thermal analysis is discussed for the flat heat pipe radiators and the cylindrical heat pipe radiators. The performance calculation is accomplished for the cylindrical heat pipe radiator, the bulk fluid and radiator fin temperature curves are presented.