Abstract: In the paper,Staphylococcus xylosus,Pediococcus pentosaceus and Saccharomyces rouxii were added as mixed fermentation strain. Based on the sensory evaluation value and amino nitrogen content,the mixing ratios of the 3 kinds of microorganisms were investigated,and the conditions of crayfish head pasta fermented by mixed strains were explored by single-factor tests and response surface methodology. The results showed that the optimal mixing ratio of Staphylococcus xylosus,Pediococcus pentosaceus and Saccharomyces rouxii was 1:3:3.The optimum autolysis condition was extracted based on the equation:Fermentation time 22.3 h,fermentation temperature 33.49 ℃,inoculation quantity 40.11 mL/kg. Under the above optimum fermentation conditions,the sensory evaluation value was 7.55 scores,and the content of amino nitrogen was(6.58±0.08) mg/mL.The umami substances of crayfish head hydrolysate before and after fermentation were analyzed by physicochemical indexs. The results showed that after fermentation,the content of taste amino acids changed little(p>0.05);the content of free amino acids was 8605.45 mg/kg,increased by 5.4%;the glycine(Gly)content of taste amino acids was 589.49 mg/kg,increased by 24.03%. The content of nucleotide related compounds before and after fermentation changed little(p>0.05). After fermentation,the content of inosine monophosphate(IMP)and guanosine monophosphate(GMP)was 3.39(increased by 31.5%)and 34.16 mg/kg respectively,which greatly contributed to toumami flavor. Crayfish head paste,prepared by microbial composite fermentation,was nutritious,full of flavor with unique and harmonious taste,and could be used as better basic material for condiment.