This application discloses a service data processing method and apparatus, to resolve a problem of low bandwidth utilization in the conventional technology. A dynamic framing method is used. When a transmission rate of an OTN data frame increases, a length of a payload area constantly increases, while a length of an overhead area does not increase. In other words, in OTN data frames at different transmission rates, lengths of overhead areas are fixed. As the transmission rates of the OTN data frames increase, lengths of payload areas constantly increase. In this way, when the rate increases, overheads do not occupy more bandwidths, thereby improving bandwidth utilization.