Abstract: An authentication system, an authentication method, and a network storage appliance are provided. The authentication system includes a client electronic device, the network storage appliance having an authentication proxy, and a directory server having an authentication service module and an account database. The client electronic device selects a data access service and transmits an encrypted data and a user data to the network storage appliance. The authentication proxy packs the encrypted data and the user data into an authentication login information and transmits the authentication login information to the directory server. The authentication service module receives the authentication login information and performs decryption and comparison on the authentication login information according to a corresponding authentication protocol and a corresponding account information in the account database, so as to determine whether the authentication is successful.