The invention relates to a synchronous information adding method and a device in a single-frequency network broadcast adapter of a digital television in the technical field of information. The method The invention relates to a synchronous information adding method and a device in a single-frequency network broadcast adapter of a digital television in the technical field of information. The methodc synchronization recovery of the single-frequency network, are simple and practical to achieve, and have flexibility and expandability.the time of synchronization and synchronization recovery of the single-frequency network, are simple and practical to achieve, and have flexibility and expandability.en the time of synchronization andin the method. The method and the device promote the occurrence frequency of the synchronous information packet in the TS stream, do not increase the burden of the prior distributing channel, shorten in the method. The method and the device promote the occurrence frequency of the synchronous information packet in the TS stream, do not increase the burden of the prior distributing channel, shortng omprises: removing a standard empty packet in TS stream, storing the TS stream after empty packet removal, monitoring the adding time of periodical synchronous information, judging an output TS packecomprises: removing a standard empty packet in TS stream, storing the TS stream after empty packet removal, monitoring the adding time of periodical synchronous information, judging an output TS packet according to the adding period of the periodical synchronous information, judging whether update exits in a memory, reading the TS packet output from the memory if the update exists, and adding thet according to the adding period of the periodical synchronous information, judging whether update exits in a memory, reading the TS packet output from the memory if the update exists, and adding theperiodical synchronous information packet output if random synchronous information packet output is added at the position capable of outputting the TS packet. The device comprises an empty packet remoperiodical synchronous information packet output if random synchronous information packet output is added at the position capable of outputting the TS packet. The device comprises an empty packet removing module, a storage module, a TS enabling control module, a synchronous information packet generating module and a TS stream output control module correspondingly achieving the information processiving module, a storage module, a TS enabling control module, a synchronous information packet generating module and a TS stream output control module correspondingly achieving the information processing