A data processing method is applied to a receiver in the field of optical transmission to implement frame synchronization. In an embodiment, a differential processing operation is introduced during frame synchronization performed by the receiver. Specifically, the receiver performs differential processing on received data after channel transmission to obtain differential data. The receiver also performs differential processing on an obtained pilot sequence to obtain a differential pilot sequence. Further, the receiver performs cross-correlation calculation on the differential data and the differential pilot sequence, and determines a frame start location in the received data based on a result of the cross-correlation calculation, to complete frame synchronization.