The present invention discloses a port automatically binding method and system. The method comprises acquiring a corresponding relation between MAC address of access switches and ports according to a MAC address list of the access switches; acquiring corresponding relations among users, IP addresses and the MAC addresses in a local area network; comprising the corresponding relation of the MAC address of each access switch and the port with the corresponding relation among the user, the IP address and the MAC address in the local area network, to obtain a corresponding relation among the user, the IP address, the MAC address and the port of each access switch; converting corresponding relation information among the user, the IP address, the MAC address and the port of each access switch into an access switch recognizable command which is then input into each access switch; and port automatically binding of the corresponding relation information among the user, the IP address, the MAC address and the port under each port by each access switch can be realized.