A scraper conveyor chain tensioning device having a sweeping function, comprising a transmission device (2), a steering chain wheel (3), scraper chains (4), and ledges (5), wherein a chain tensioning device (1) is arranged above the scraper chains (4) arranged at the side of the steering chain wheel (3), the chain tensioning device (1) is provided with a sweeping device (12), the chain tensioning device (1) comprises a slider-crank mechanism and two chutes (13) symmetrically fixed to the ledges (5) on two sides at an inclined angle, a tensioning shaft (19) is arranged between the two chutes (13), the tensioning shaft (19) is arranged on a bearing seat (18) via a bearing, and the middle part of the tensioning shaft (19) is provided with a tensioning chain wheel (11) matching with a transmission chain; and the sweeping device (12) comprises a tensioning shaft sleeve (12-3), a plurality of groups of sweeping heads (12-2) is arranged on the circumference of the tensioning shaft sleeve (12-3) at intervals, and the sweeping heads (12-2) are fixed to the tensioning shaft sleeve (12-3) via springs (12-1). Caking coal on a scraper can be swept via scraping teeth on sweeping heads (12-2), the problems of friction, chain jumping and jamming caused by the caking coal on the scraper are solved, the scraper conveyor chain tensioning device is applicable to a middle double-chain scraper conveyor, the change on an original scraper conveyor is small, and pure mechanical transmission is adopted, thereby being simple in mechanism, convenient to assemble and disassemble, and reliable in operation.