Abstract: By using Candida utilis and bacteria M2 that was isolated from cottonseed shell to be solid- state fermentated cottonseed meal.Molecular identification showed that M2 was Klebsiella oxytoca and the login number was KT962208 in the NCBI.By using the two factors have repeated observation value test and uniform design test of DPS v7.05 statistical software to respectively optimize inoculum and inoculation ratio,and the fermentation temperature,time and initial containing water of solid state fermentation.And analyzed these experimental data.Finally,come to the conclusion that the best inoculation amount was 4 m L /100 g and the inoculation ratio of Candida utilis yeast and M2 was 7 ∶ 3,the fermentation temperature was 32.5 ℃,time was 54 h,initial containing water was 75%. Under this kind of condition,the degradation rate of gossypol was 53.021%,the crude protein content was 45.889%,and the molecular weight of the protein has slightly decreased.