A system and method of dynamic routing is provided. When a connection cannot be built, execute the follows. (a) A sending-host transports messages to destination-host. If connection built, the method ends, otherwise go to step (b). (b) Find a series of routers, and put IP-addresses of routers into a list. (c) Judge whether list includes at least one IP-address; if yes, go to step (d), otherwise step (i). (d) A pointer points to the last. (e) Find a domain of IP-address pointed. (f) If a message-routing-in-charge host is found, go to step (g), otherwise step (h). (g) The sending-host transports messages to message-routing-in-charge host, and go to step (a). (h) If IP-address pointed is the first one, go to step (i), otherwise step (j). (i) The sending-host keeps messages for a period, and go to step (a). (j) Move pointer to point to the previous, and go to step (e).