Embodiments of this application provide a method for receiving and sending a reference signal, an apparatus, and a system, so that a network device can correctly demodulate uplink data of different terminal devices of a same cell. This solution is applicable to a wireless communications system including a first cell. The first cell includes a plurality of terminal devices that can transmit uplink data on a same time-frequency resource. A first terminal device in the plurality of terminal devices determines an index of a first sequence based on a first parameter value, and generates a first reference signal based on the first sequence indicated by the index of the first sequence. Then, the first terminal device sends the first reference signal to the network device. The first parameter value is different from a parameter value corresponding to another terminal device in the plurality of terminal devices.