The invention discloses a method for achieving unvarnished transmission of a timestamp on the basis of a network system which is formed by a client connected with a background server through the Internet and a four-layer proxy server under the condition that the system runs under an SYN Cookie/SYN Cache mechanism. The method mainly comprises the process as follows: the client sets a TCP timestamp option to be zero in transmission control protocol (TCP) connection handshake with the background server through the internet and the four-layer proxy server. Compared with the prior art, by adopting the method disclosed by the invention, the performance of the four-layer proxy server is improved, and design and achievement of supporting the timestamp option by the four-layer proxy server are simplified.