A beam training method includes: determining, by a terminal device, to send n pilot sequences to a network device by using n beams in n timeslots within one uplink beam training period, where the n pilot sequences are at least partially different, and n is a positive integer greater than 1; and sending, by the terminal device, the determined n pilot sequences to the network device by using the n beams in the n timeslots within the uplink beam training period.