Abstract: Study of communication satellite(CS)s reliability not only could help to solve its engineering problems but also would play an important role for long-life spacecraft engineering.On the basis of wide researching the information on communication satellites home and abroad,the works on surveying their performances on orbit and analysing the elements which influence their life and reliability have been done.Space environment is the important one in these elements. The study of methods for reducing or avoiding its effects,that is "spacecraft immunity engineering for environment",has also been done.Other design strategies for long-life spacecraft have been studied. The design experience has been synthesized and the subjects which need further study have been searched.