An optical transmission system and transmission method, an optical switching apparatus, and a control method are provided. Any data transmission apparatus included in an optical transmission system is configured to: transmit an optical label signal and a continuous data signal including an idle sequence and a data packet, and transmit the transmitted optical label signal to an optical switching apparatus, so that the optical switching apparatus builds, according to the optical label signal, a switching and transmission path for transmitting the continuous data signal transmitted by the any data transmission apparatus. This ensures that a data transmission apparatus transmits a continuous data signal, and also ensures that each optical receiving system can receive the continuous data signal. Therefore, no preamble needs to be added before a data packet carried in a to-be-processed data signal, thereby avoiding a resource waste and saving bandwidth resources.