A data synchronization method includes: receiving time interval information sent by a second terminal device, where the time interval information includes a synchronization start time and a synchronization end time; obtaining, in stored waking and sleep time information, a time period set that is greater than or equal to the synchronization start time and that is less than or equal to the synchronization end time, where the time period set includes at least one sleep time period; determining, in the time period set, a sleep time period whose sleep duration is greater than a preset threshold; and sending, to the second terminal device, feature data collected in the determined sleep time period.