This application discloses a reference signal determining method and an apparatus. The method includes a first device determines a first reference signal sequence in a reference signal sequence set. The first device maps the first reference signal sequence to a first symbol sequence, and sends a first reference signal corresponding to the first reference signal sequence to a second device based on the first symbol sequence. The first reference signal sequence is used by the second device to estimate impact of phase noise on a received signal, and the impact of the phase noise on the received signal includes at least one of inter-subcarrier interference, a common phase error, and the phase noise. The reference signal sequence set includes at least a first-type reference signal sequence. A time-domain amplitude variance and a frequency-domain amplitude variance of the first-type reference signal sequence each meet a preset threshold.