The present invention discloses a method for multiplexing data stream, including the following steps: a transmission terminal transmits random value and destination UDP port number to a receiving terminal, and takes the random value as multiplexing ID of a multiplexing message which is transmitted to the receiving terminal; the receiving terminal establishes the mapping relation of the random value and destination UDP port number, and receives multiplexing message according to established mapping relation. The present invention also discloses a transmitting data stream multiplexing device, a receiving data stream multiplexing device as well as a data stream multiplexing system. The present invention takes a random value as multiplexing ID of multiplexing message, and makes the random value be carried in a message to transmit to a receiving terminal when transmitting multiplexing initialization message, then establishes the mapping relation of the multiplexing ID and destination UDP, which improves the reliability and transmission efficiency of the data stream multiplexing technology.