Abstract: Identity authentication is a very important aspect of information security theory. Usually, the common problem with identity authentication is that the user's name and password are transmitted in the network in plaintext, which is not safe, and vulnerable to replay attacks and dictionary attacks. Although dynamic passwords authentication is more secure, if there is a problem with the time synchronization between the server and the client, the user will not be able to login for a long time. Moreover, most password of the dynamic password is the same within a period of time, and it is also vulnerable to replay attacks. Therefore, a decentralized dynamic identity authentication system based on blockchain is proposed. By using a public key+nonce (integer number that increases from 0) to sign in, it not only solves the problem of over-centralized identity authentication, but also solves the replay attack. The proposed system improves the security of the identity authentication process.