The invention discloses a pesticide leftover detection device for a crop drier. The pesticide leftover detection device comprises a detection tube and a pesticide detection device arranged inside the detection tube, wherein the detection tube is movably arranged inside a feeding hole of the crop drier; the pesticide detection device comprises an upper conveyor belt, a lower conveyor belt, a detection liquid box, a recycling liquid box, a cleaning liquid box and an electric control box, and detection test paper is arranged on the upper conveyor belt in an adhered manner; the detection liquid box, the recycling liquid box, the cleaning liquid box and the electric control box are arranged between the upper conveyor belt and the lower conveyor belt, and a linear stepping motor and a crop collection box are arranged on the side, away from the upper conveyor belt, of the lower conveyor belt. Pesticide detection and drying of crops can be carried out synchronously, so that the time is saved extremely; and through the crop collection box driven by the linear stepping motor, crops of which pesticide leftovers exceed standard can be found out after detection, so that the crops of which the pesticide leftovers exceed the standard cannot be mixed with normal crops after drying, and crop quality cannot be influenced.