An authentication system, characterized by comprising: a client electronic device, receiving a password and a user data input by a user, wherein the password and the user data are corresponding to an account database; a network storage appliance, having an authentication proxy, wherein the network storage appliance is a storage appliance adopting a network attached storage, NAS, technique; and a directory server, connected to the network storage appliance via an Ethernet connection, having an authentication service module, and comprising the account database, wherein the client electronic device selects a data access service and transmits an authentication request to the network storage appliance, wherein the network storage appliance receives the authentication request, selects an authentication protocol according to the authentication request, and transmits at least one parameter required by the authentication protocol to the client electronic device, and wherein the client electronic device transmits a first encrypted data and the user data required by the authentication protocol to the network storage appliance, wherein the client electronic device encrypts the parameters and the password to generate the first encrypted data, and the authentication proxy of the network storage appliance packs the first encrypted data and the user data into an authentication login information according to a type of the authentication protocol and transmits the authentication login information to the directory server, wherein the authentication service module of the directory server receives the authentication login information and performs decryption and comparison on the authentication login information according to the type of the authentication protocol and a corresponding account information in the account database, so as to determine whether an authentication is successful, and then the authentication service module transmits an authentication response to the network storage appliance. a client electronic device, receiving a password and a user data input by a user, wherein the password and the user data are corresponding to an account database; a network storage appliance, having an authentication proxy, wherein the network storage appliance is a storage appliance adopting a network attached storage, NAS, technique; and a directory server, connected to the network storage appliance via an Ethernet connection, having an authentication service module, and comprising the account database, wherein the client electronic device selects a data access service and transmits an authentication request to the network storage appliance, wherein the network storage appliance receives the authentication request, selects an authentication protocol according to the authentication request, and transmits at least one parameter required by the authentication protocol to the client electronic device, and wherein the client electronic device transmits a first encrypted data and the user data required by the authentication protocol to the network storage appliance, wherein the client electronic device encrypts the parameters and the password to generate the first encrypted data, and the authentication proxy of the network storage appliance packs the first encrypted data and the user data into an authentication login information according to a type of the authentication protocol and transmits the authentication login information to the directory server, wherein the authentication service module of the directory server receives the authentication login information and performs decryption and comparison on the authentication login information according to the type of the authentication protocol and a corresponding account information in the account database, so as to determine whether an authentication is successful, and then the authentication service module transmits an authentication response to the network storage appliance.