Abstract: The popularization of the computer, development of the network have already brought the mankind into information society, information is playing an important role in the human society. The importance of the information also has decided the necessity of information security defense. The information security can be considered from three respects that, namely the network security, the system are safe and information stores safely. This paper discussd the problems about memory security, and discussed the (basic) requst of memory security and the essential countermeasure correspondingly. As the application this paper analysed the mentality of designing about the “file safe” and “the tool for file deletion”, and introduced their implementation methods.