Abstract: A turbid solution was formed through the reaction between γ-PGA and Cetyl Trimethyl Ammonium Bromide (CTAB) sodium hydroxide solution, the preparation of different concentrations of γ-PGA standard solution with CTAB solution to form a reaction system, and the formation to make a full wavelength scan, draw the standard curve of different wavelengths, and CTAB reagent concentration, reaction time and temperature on the reaction system were optimized.The results showed that CTAB turbidimetry best detection wavelength was 250nm, CTAB mass concentration of 5g/L, reaction temperature was room temperature, complexing 3min.The linear regression equation y=0.0335x-0.1519, R2=0.9995.The precision and recovery of this method were within 2.56% and 106.6%.The turbidimetric method has advantages of convenience, simplicity and good repeatability and can be used to detect the γ-PGA concentration in the fermentation broth.