The application discloses an IP address conversion method, routing equipment and a communication system, relating to the field of communication, and aiming at implementing the normal communication ofrouters that do not support the same network segment of a WAN port but are assigned with the same public network IP network segment. The method includes the following steps: when performing NAT services, enabling the routing equipment to send a first message to an opposite terminal through the WAN port, and converting a virtual IP address that represents a source IP address of the message in the first message into a public network IP address; receiving a second message from the opposite terminal through the WAN port; converting the public network IP address of the second message into a corresponding virtual IP address that represents a destination IP address of the message; when performing ARP services, sending a third message to the opposite terminal through the WAN port, and converting avirtual IP address that represents the source IP address and the destination IP address of the message in the third message into the corresponding public network IP address; and receiving a fourth message from the opposite terminal through the WAN port, and converting the public network IP address of the fourth message into a virtual IP address that represents the source IP address and the destination IP address of the message. The embodiment of the application is applied to the routing equipment at the WAN port of the same network segment.