The invention discloses a dyeing technology of cotton loose fiber. The technological process comprises the steps of assorting cotton, bleaching, whitening, dyeing, washing, carrying out soap boiling, oiling for color fixation, dehydrating, drying and packaging. After the dyeing technology is adopted, cotton yarn has richer color layers and the hazy feeling, and the chromatic aberration of the yarn can be reduced. After being dyed, cotton with different colors can be mixed for spinning and weaving according to the specific proportion, so that bright and colorful melange yarn with unique style can be obtained, and the additional value of the yarn is greatly improved.