Example radio link monitoring methods and apparatus are described. One example method includes performing radio link monitoring (RLM) in a second bandwidth part (BWP) by a terminal device. The terminal device receives first switching information from a network device that is used to indicate that an active BWP includes a first BWP, and switches from the second BWP to the first BWP based on the first switching information. The terminal device removes a measurement result obtained by performing RLM in the second BWP, where the measurement result includes a quantity N1 of one or more out of synchronization (OOS) states or a quantity N2 of one or more in synchronization (IS) states. RLM is performed in the first BWP.