Disclosed are a signal transmission method, a terminal device and a network device. The method comprises: the terminal device detects downlink control information (DCI) on a physical downlink control channel (PDCCH), the DCI being used for scheduling transmission of a signal on a first physical resource; if the DCI is detected by the terminal device, the terminal device does not detect a synchronizing signal block on the first physical resource. Therefore, when the DCI is detected by the terminal device, the terminal device may not detect the synchronizing signal block on the first physical resource scheduled by the DCI, so as to reduce detection complexity of the terminal device on the synchronizing signal block.