The present disclosure discloses a method and system for restarting the network service with zero downtime, comprising: a) listening, by an original process of the network service, on a first port; (b) configuring and initiating a transition process, wherein the configuring includes causing the transition process to listen on a second port different from the first port of the original process; (c) running a connection tracking module and, meanwhile adding an iptables rule to redirect a connection directed to the first port to the second port; (d) waiting until existing connections on the original process are processed completely, then exiting the original process; (e) initiating a new process on the first port according to a new configuring file; (f) reconfiguring the iptables rule to cancel port redirection; and (g) waiting until existing connections on the transition process are processed completely, then exiting the transition process.