The invention relates to a drug drying device and particularly relates to a grading-type drying device. The grading-type drying device comprises a box body, wherein a feeding hole is formed in the top of the box body; a discharging hole is formed in the bottom of the box body; a plurality of horizontal conveying belts parallel to one another are arranged in the box body; the conveying belts at odd positions are arranged near the left side wall of the box body from the top to the bottom and rotate rightwards; the conveying belts at even positions are arranged near the right side all and rotates leftwards; sieve holes are formed in each conveying belt; the number of the sieve holes in the conveying belts is gradually increased from the top to the bottom; an air heater connected with the interior of the box body is arranged at the bottom of the box body; an exhaust pipe is arranged at the top of the box body. The grading-type drying device has the beneficial effects that the drying efficiency is improved, and the production cost is saved.