For high safe and high efficiency encryption system was designed by using the negative selection algorithms of Artificial Immunity Theory, and its safe was demonstrated. It is a new method based on the negative selection algorithm and extracts the encryption factor from the plaintext. Encryption factor as a key group is expanded by the way of the m-sequence and generates pseudo-random key sequence that can be used to encrypt data. Pseudo-random key sequence generated in this way has good characteristics of self-correlation and the encrypted data has a better anti-attack performance. Therefore, there will be a good prospect of application.