Abstract: This study aimed to enhance the quality of cottonseed meal through solid-state fermentation. The effects of sensory evaluation, anti-nutritional factors, crude protein, total acid and acid-soluble protein after fermentation were investigated. Bacillus subtilis was employed for the degradation of anti-nutritional factors, and the optimum conditions for inoculation amount, water-material ratio and fermented time were determined. The results showed that, when the optimum amount of inoculation was 11%, the optimum ratio of water to material was 0.6%—0.8%, and the degradation rate of anti-nutritional factors reached the highest when the fermentation time reached 60h. Then mixed solid-state fermentation was carried out by using Saccharomyces cerevisiae, Lactobacillus plantarum and Bacillus subtilis plus phytase and cellulase, and the optimum proportion of mixed bacteria and enzyme solution was identified. The results demonstrated that a 1﹕1﹕2 ratio of Bacillus subtilis, Saccharomyces cerevisiae and Lactobacillus plantarum, combined with 1.25% cellulase and 0.10% phytase, achieved the highest degradation of anti-nutritional factors. Furthermore, the sensory evaluation of cottonseed meal after mixed bacteria fermentation was better than that of single bacteria fermentation. The degradation rate of free gossypol and phytic acid reached 40.13% and 34.92%, respectively, while tannin degradation rate was 40.24%. Additionally, the crude protein, acid-soluble protein and total acid increased by 10.26%, 59.2% and 79.49%, respectively. This study provides a reference for improving the nutritional value of cottonseed meal and supports its use as a plant protein source in aquafeeds.