A method and apparatus for multiplexing demodulation reference signals and a communication system. The method for multiplexing includes: transmitting data and DM-RSs by using one or more time-frequency resource blocks; the DM-RSs of each UE or each data stream occupy a part of frequency-domain resources of the time-frequency resource blocks, the DM-RSs of a part of UEs or data streams are superimposed on identical time-domain resources in a manner of frequency-division multiplexing, and the DM-RSs of a part of the UEs or data streams are superimposed on identical time-frequency resources in a manner of code-division multiplexing. Hence, even if in a case of massive UEs access, the DM-RSs may be multiplexed within given time-frequency resources, while performance of transmission may still be ensured.