Vigenere encryption algorithm is a very well-known multi-code encryption, in fact, it is the simplified form of auto-key cryptography , it is based on key words, but it is not defined as using keywords like single-code keywords addition to the replacement in the form.This is the alternative of a multi-table encryption password can be encrypted with different passwords on the same information in different letters. Only in this way, the same character "E" in one location may be replaced by the character "M" and in another location the characters "E" may be another character "K" replaced. It can prevent any person from using frequency analysis to decrypt the article information, but also to make up for the defects of the frequency analysis method is very easy to crack the longer the length of ciphertext.