The invention discloses a real-time multimedia data transmission method for supporting NAT traversal, which comprises the following steps of: (1) creating a UDP socket on an NSPC, randomly binding a port for the socket, recording the number value of the port as G-Port, judging the NAT type of a client of the NSPC by using the socket through the NSPC, and establishing an NAT traversal channel between the NSPC and other NSPC; (2) during sending data, acquiring data message of an upper application program through the NSPC, searching an NSPC socket control list, retrieving a socket to which the message belongs and an NAT address of a receiving end, finishing encapsulation of the message and sending the message to a network; and (3) during receiving the data, acquiring UDP data message reaching the port G-Port through the NSPC, judging whether the message is subjected to the NSPC encapsulation, if so, removing the encapsulation of the message, pushing the data to a corresponding application program and waiting for further processing.