The invention discloses a grate-layer material separating device for a sintering machine. The grate-layer material separating device comprises a supporting plate, a retaining plate, a portal frame, aseparating chute and a lifting device; the portal frame is arranged over a first-stage or second-stage grate-layer material returning belt; the retaining plate is installed on the portal frame throughthe lifting device; after being lifted down by the lifting device, the retaining plate is just positioned on the first-stage or second-stage grate-layer material returning belt and is used for separating grate-layer materials on the first-stage or second-stage grate-layer material returning belt; the supporting plate is arranged at the downstream side of the retaining plate through a mounting bracket and is used for supporting the retaining plate; a feeding opening of the separating chute is formed at the retaining plate and is used for receiving the grate-layer materials separated by the retaining plate; and a discharging opening of the separating chute faces to a grate-layer material supply belt of a trolley of a second-stage or first-stage sintering machine. The grate-layer material separating device disclosed by the invention greatly shortens the dry-burning time when the first-stage or second-stage sintering machine starts to work after being overhauled and greatly improves the sintering efficiency and greatly reduces the ore return ratio, and meanwhile the amount of replaced grate bars in every overhauling time is about 800 and is reduced by 90%.