In an uplink synchronization method, a network device may send a timing advance (TA) of a normal uplink (NUL) and a TA of a supplementary uplink (SUL) to a terminal device. The terminal device may adjust, based on the TA of the NUL, time for sending uplink data through the NUL, and adjust, based on the TA of the SUL, time for sending data through the SUL. The terminal device may separately adjust the time for sending uplink data through the NUL and the time for sending uplink data through the SUL.