Provided is a tracking control system for a long-distance belt conveying line. The long-distance belt conveying line is composed of a plurality of belt conveyor sections. The tracking control system comprises an information processor, mirror reversal photoelectronic devices installed on side plates at the tails of the belt conveyor sections correspondingly, and code disk signal detection devices installed on power shafts of the belt conveyor sections correspondingly. Each code disk signal detection device comprises a mechanical code disk and a proximity switch. The information processor is used for establishing a data storage area for each belt conveyor section so as to record mail data of the belt conveyor section, and the mail data comprise the information, such as the time, time interval, mail length, unique tracking code and current position, of each mail having access to the belt conveyor section. The information processor is used for prejudging when and where each mail enters the next belt conveyor section.