The invention discloses a waterless fiber dyeing method using supercritical carbon dioxide fluid as a medium. Dry fibers are tightly loaded layer by layer in a porous yarn cage. After dyeing, the fibers are cleaned to remove unfixed dyes by an online way, thereby obtaining waterless dyed dry fiber products with good quality. With the supercritical carbon dioxide dyed by a dye, the invention can not only solve the problems of high energy consumption, high discharge, high pollution in the traditional dyeing process, but also obtain better dyeing effect. The invention has a simple process and convenient operation, which can effectively realize dry dyeing processing. The reaction is mild, avoiding the use of a large amount of water, heat and additives in high concentration, which has the features of being high efficiency and environmentally friendly.