The invention discloses an access method employing network address translation (NAT) device for supporting multi-networking and a device thereof. The method comprises the following steps: the NAT device records the networking topological type and NAT rules of an side interface on each public-network side of the device; the NAT device receives a message sent from a host computer in a private network to a server in a public network, confirms the outgoing interface of the message and forwards the message according to the networking topological type and NAT rules of the side interface. The invention realizes the access between the private network and the public network by adopting the NAT device to support the multi-networking.