Embodiments of this application disclose a signal transmission method, a terminal device, and a network device. The method includes: determining, by a terminal device, information indicating a channel state information-reference signal (CSI-RS) resource, the information corresponding to a target uplink signal; determining, by the terminal device, a power control parameter of the target uplink signal according to the information indicating the CSI-RS resource; determining, by the terminal device, a transmit power of the target uplink signal according to the power control parameter; and sending, by the terminal device, the target uplink signal to the network device according to the transmit power. The method, the terminal device, and the network device in the embodiments of this application help improve the accuracy of power control, so that system transmission performance can be improved.