This application discloses a channel estimation method, a reference signal sending method, an apparatus, and a system, and belongs to the communications field. The method includes: when a first precoding weight of a first reference signal and a second precoding weight of a second reference signal are the same, receiving, by a first network device, the first reference signal in a first time unit according to a first pattern, and receiving the second reference signal in a second time unit according to a second pattern; and performing, by the first network device, channel estimation on a channel in the second time unit.