The invention relates to a device and method for converting positive and negative rotation input into single-direction output and belongs to the technical field of mechanical transmission. According to the technical scheme, a first end cover (1) and a second end cover (8) are arranged at the two ends of an outer sleeve (2). A first gear (3), a second gear (4) and an anticlockwise ratchet wheel (5)are sequentially arranged between the part, close to end with the first end cover (1), of the outer sleeve (2) and an inner sleeve (9). The first gear (3) is engaged with the inner gear ring of the outer sleeve (2) and the second gear (4). The second gear (2) is connected to the anticlockwise ratchet wheel (5) which is connected to the inner sleeve (9). A spline sleeve (6) and a clockwise ratchetwheel (7) are sequentially arranged between the part, close to the end with the second end cover (8), of the outer sleeve (2) and the inner sleeve (9). The clockwise ratchet wheel (7) is connected tothe inner sleeve (9), and the spline sleeve (6) is connected with the outer sleeve (2) through a spline. The device and method have the beneficial effects that positive and negative rotation input can be converted into single-direction output, the structure is simple, and reversing is stable.