A network authentication method, a client and a device are provided. The method includes: receiving SYN data sent by a client, where the SYN data includes a sequence number SEQ1 and a network parameter comprising an ID in the header of the SYN data; sending SYN_ACK data to the client, where the SYN_ACK data includes an acknowledgment number ACK2 obtained by carrying out a function transformation according to the network parameter; receiving RST data sent by the client, where the RST data includes a sequence number SEQ3 or an acknowledgment number ACK3, and the RST data further includes a network parameter the same as that of the SYN data; carrying out the function transformation according to the network parameter of the RST data to obtain a check value CHK; and passing the authentication of the client if CHK matches SEQ3 or ACK3.