A communications method and apparatus are provided. The method includes: A first terminal side device determines a frequency domain resource of a scheduled first physical downlink shared channel (PDSCH), where the first PDSCH corresponds to a first demodulation reference signal (DM-RS) on a first antenna port; and when the frequency domain resource includes N consecutive frequency domain units, and there is a second DM-RS on a second antenna port in each of L consecutive frequency domain units in the N frequency domain units, determines that precoding of each second DM-RS is the same. The second DM-RS and the first DM-RS are in a same code division multiplexing (CDM) group, the second DM-RS corresponds to a second PDSCH scheduled for a second terminal side device, each N and L is an integer greater than 1, and L is less than or equal to N.