Abstract: Yellow water, one of the by-products of Baijiu brewing. Microbial fermentation to produce γ-PGA using yellow water as substrate. This idea not only finds a new way for the comprehensive utilization of yellow water, but also realizes the high value utilization of yellow water. In this paper, the liquor by-product yellow water as the substrate for microbial fermentation, optimizing the culture medium and conditions of fermentation synthetic γ-PGA using single factor and response surface design experiments. Fermentation results were evaluated by measuring γ-PGA concentration, viscosity, residual glutamate and glucose concentration in fermentation broth. According to the results, when the pH value was 7.0 and the yellow water was diluted 7 times, Corn saccharification solution 75 g/L (by soluble solids content), Beef powder 70 g/L, Sodium glutamate 45 g/L, NaCl 12 g/L, K₂HPO₄ 7 g/L, the inoculation amount was 1%, 25 mL/250 mL, at 37 ℃ for 72 h, the yield of γ-PGA was 14.510 g/L. Hence, it is feasible to synthesize γ-PGA by microbial fermentation using yellow water as the substrate.