A signal transmission method includes: determining, by a terminal device, at least one start time point for entering an activated state of radio resource control (RRC) active discontinuous reception (DRX); and receiving, by the terminal device at each of the at least one start time point, a first signal sent by a network device, the first signal being used by the terminal device to determine, from at least one downlink receiving beam, a target downlink receiving beam for receiving and decoding a downlink control channel sent by the network device.