Computer security has always been the one that is an important and serious issue. The stability of the running program design often becomes important for judging the success. The stability of the code is not only a security issue, or computer programming is crucial and related areas of basic research is important. This article introduced the concept of stability of the significance and importance in the programming position, and stability analysis procedures. Clarified the relationship of code fault-tolerance programming with code security. For the code running state in the four-levels proposed on the stability, and the article presented more details the concept of fault-tolerant level with the typical model. Believe that with the attention degree of the code to improve stability, security and stability of the technology program will be vigorously the development and strengthening.