Example beam training methods and apparatus are described. In one example method, a first terminal apparatus sends a first message to a second terminal apparatus, where the first message includes a request for a first list, the first list includes an identifier of at least one sidelink synchronization signal, and the at least one sidelink synchronization signal is a sidelink synchronization signal that is not used by the second terminal apparatus within a preset time range and/or that is not used by another terminal apparatus within an area in which the second terminal apparatus is located. The first terminal apparatus receives a second message from the second terminal apparatus, where the second message includes the first list. A first sidelink synchronization signal is determined based on the identifier of the at least one sidelink synchronization signal in the first list. The first sidelink synchronization signal is used for beam training.