A reference signal transmission method and an apparatus are provided and relate to the field of communication technologies, so that accuracy of channel estimation can be improved while a quantity of antenna ports is increased. The method includes: determining, based on a frequency-domain channel matrix associated with an antenna port and a frequency-domain sampling number of a reference signal associated with the antenna port, a frequency-domain resource mapping relationship for the reference signal; sending first information to a receiver device, where the first information indicates the frequency-domain resource mapping relationship for the reference signal; and sending or receiving the reference signal based on the frequency-domain resource mapping relationship for the reference signal.