The invention provides a detecting system for roller breakage in a roller kiln. The detecting system comprises a plurality of groups of roller groups, wherein each roller group comprises two or more conveying rollers which are sequentially adjacent; all the roller groups are correspondingly equipped with two groups of optical transceiver assemblies connected with a monitor; light-shielding parts used for alternately shielding detecting light paths of the two groups of optical transceiver assemblies are connected with the driven ends of all the conveying rollers; a sealing cover, correspondingto each roller group, is arranged outside a furnace body; a sealed cavity is encircled by each sealing cover and the furnace wall of the furnace body; the driven ends of all the conveying rollers penetrate through the furnace wall and extend into the corresponding sealed cavities; the light transceiver assemblies comprise light transmitters, light receivers and reflector groups; the reflector groups are mounted in the sealed cavities; the light transmitters and the light receivers are mounted above or below the sealing covers; the sealing covers are equipped with first transmission windows andsecond transmission windows; and the detecting light paths are formed between the reflector groups. The detecting system has the advantages that the mounting, the debugging and the maintenance are simple and convenient; the sealing performance can be improved; the working stability and reliability are high; and the service life is long.