The invention discloses a printing and dyeing method for cotton fibers. The method is to successively subject the cotton fibers to enzyme treatment, washing, drying, dip dyeing and dye fixation, wherein enzyme treatment is carried out under the action of supersonic waves with a frequency 150 to 160 KHz, and enzyme used in enzyme treatment is pectase. With the method provided by the invention, time for enzyme treatment is shortened for 10 to 15 min compared to original 1 h or so; and the cotton fibers treated by using the method have obviously improved capillary effects and enhanced color fasteness because of cavitation of the supersonic waves.