A signal transmission method, performed by a user equipment, comprising: receiving a first reference signal sent by a network device wherein the first reference signal is a precoded reference signal precoded using a precoding matrix determined according to downlink channel coefficients obtained from uplink channel measurements of a sounding reference signal, SRS, signal, transmitted by the user equipment; measuring the first reference signal to obtain a measurement result; determining a mapping relationship from each of multiple mapping relationship sets according to the measurement result, wherein the multiple mapping relationship sets comprise a first relationship set and at least one of a second relationship set and a third relationship set, the first relationship set comprises multiple mapping relationships between a codeword and transmission layer when a quantity of transmission layers is determined, the second relationship set comprises multiple mapping relationships between the transmission layers and a demodulation reference signal DM-RS port, and the third relationship set comprises multiple mapping relationships between the transmission layers and a channel state information-reference signal CSI-RS port; and sending a notification message to the network device, wherein the notification message is used to indicate the determined mapping relationships; wherein determining a mapping relationship from the second relationship set comprises: obtaining signal-to-noise ratios corresponding to an effective channel corresponding to each DM-RS demodulation pilot port, each effective channel being the product of the downlink channel coefficients and the precoding matrix, selecting two or more DM-RS demodulation pilot ports based on signal-to-noise ratios and mapping individual layers to selected DM-RS demodulation pilot ports; and wherein determining a mapping relationship from the third relationship set comprises: traversing mapping relationships between each transmission layer and different CSI-RS configurations selected from two or more CSI-RS configurations and selecting a mapping relationship between a transmission layer and a CSI-RS configuration with maximum signal-to-noise ratio, and wherein the first reference signal comprises CSI-RSs and corresponds to said two or more CSI-RS configurations. receiving a first reference signal sent by a network device wherein the first reference signal is a precoded reference signal precoded using a precoding matrix determined according to downlink channel coefficients obtained from uplink channel measurements of a sounding reference signal, SRS, signal, transmitted by the user equipment; measuring the first reference signal to obtain a measurement result; determining a mapping relationship from each of multiple mapping relationship sets according to the measurement result, wherein the multiple mapping relationship sets comprise a first relationship set and at least one of a second relationship set and a third relationship set, the first relationship set comprises multiple mapping relationships between a codeword and transmission layer when a quantity of transmission layers is determined, the second relationship set comprises multiple mapping relationships between the transmission layers and a demodulation reference signal DM-RS port, and the third relationship set comprises multiple mapping relationships between the transmission layers and a channel state information-reference signal CSI-RS port; and sending a notification message to the network device, wherein the notification message is used to indicate the determined mapping relationships; wherein determining a mapping relationship from the second relationship set comprises: obtaining signal-to-noise ratios corresponding to an effective channel corresponding to each DM-RS demodulation pilot port, each effective channel being the product of the downlink channel coefficients and the precoding matrix, selecting two or more DM-RS demodulation pilot ports based on signal-to-noise ratios and mapping individual layers to selected DM-RS demodulation pilot ports; and wherein determining a mapping relationship from the third relationship set comprises: traversing mapping relationships between each transmission layer and different CSI-RS configurations selected from two or more CSI-RS configurations and selecting a mapping relationship between a transmission layer and a CSI-RS configuration with maximum signal-to-noise ratio, and wherein the first reference signal comprises CSI-RSs and corresponds to said two or more CSI-RS configurations.