The invention provides a communication design method based on auto-negotiation IP addresses. The method comprises the following steps: two devices each generate a random number and exchange the random numbers with each other; the two devices perform calculation on the generated random numbers and the received random numbers to get new values, which are recorded as A and B respectively; if A and B are the same, the two devices regenerate random numbers and perform calculation until A and B are different; the devices notify each other that random number exchange is completed; the IP address of the local device and the IP address of the opposite device are generated, and the two addresses are respectively saved to respective BUFs; the side actively initiating communication in the two devices reads the IP address of the local device and the IP address of the opposite device from the BUF, and replaces the destination IP address and the source IP address in a communication data packet. The problem that the IP addresses must be set manually during communication of two point-to-point devices via a TCP/IP protocol is solved. The operation complexity is reduced. The convenience in use of communication devices needing to be switched between different network environments is improved especially.