Abstract: The present invention relates to a method and an apparatus for dyeing cotton at fiber stage and a method for preparing yarn. The present invention provides an apparatus (100) for dyeing fibers and filaments comprising plurality of pre-wetting troughs (18), plurality of dye baths (20), and a drying arrangement (22) characterized in having a supporting system (14) for carrying and dyeing the fiber (12) continuously and homogeneously. The fibers or filamnents for dyeing includes cotton and other natural fibers, man made and synthetic fibers as well as filamnents and a combination thereof. The fiber for dyeing according to the present invention is cotton fiber.