The invention discloses a road surface slope gradient detection device which comprises a bottom plate, a detection unit, a replacement unit, a fixing frame and a push handle; a fixing frame is arranged at the top end of the bottom plate, a push handle is arranged on the right side of the top end of the bottom plate, a cleaning unit is arranged on the front side of the top end of the bottom plate,and a shading unit is arranged at the top end of the fixing frame. The detection unit comprises a connecting plate, a rotating shaft, a fixed block, a T-shaped block, a pointer, a supporting rod and adial, the connecting plate is arranged at the top end of the interior of the fixing frame; the front side surface of the connecting plate is rotationally connected with the rotating shaft; the fixedblock is arranged at the front end of the rotating shaft; a T-shaped groove in the bottom end of the front side face of the fixed block is matched with the T-shaped block, the pointer is arranged at the bottom end of the T-shaped block, the supporting rod is arranged on the rear side face of the dial, and the left end and the right end of the supporting rod are connected with the left side and theright side of the interior of the fixing frame correspondingly. The road surface slope gradient detection device is simple to use and easy to move, has various functions and good detection effect.