A signal transmission method and an apparatus are provided. The method includes: A sending device generates a sequence of a demodulation reference signal, and maps the sequence of the demodulation reference signal to a time-frequency resource of the demodulation reference signal for sending. The demodulation reference signal is used to estimate a channel state of a first channel, and the first channel carries uplink data. The time-frequency resource includes frequency-domain resources corresponding to a first CDM group, and the frequency-domain resources corresponding to the first CDM group are non-contiguous and equally spaced.