Yellow water, the main by-product of Baijiu brewing, was rich in a variety of organic matter. It can be used to prepare esterification liquid, which can promote the aroma of Baijiu, and improve its utilization. Monascus sanguineus X1, a high esterifying enzyme-producing strain, was used to optimize the enzyme activity by single factor and orthogonal experiments from four aspects:carbon source, carbon-nitrogen ratio, inoculation amount and pH. Then, the esterifying solution was prepared by treating the yellow water with an esterifying enzyme solution, and the influence of the addition amount of the esterified precursors such as yellow water, ethanol and caproic acid on the preparation of the esterification liquid was studied. The results showed that the optimum fermentation medium for Monascus was (per 100mL) rice flour 7.0g, soybean peptone 2.0g, NaNO₃ 0.2g, KH₂PO₄ 0.15g, MgSO₄·7H₂O 0.1g, initial pH 5.0 and inoculation volume 10% (volume fraction). Under these conditions, adding 10% yellow water by volume and 4% ethanol by volume, the enzyme activity could reach 745.80U/mL. After adding 0.8% caproic acid and 20% ethanol by volume to the esterifying enzyme solution for 1 day, the volume fraction of ethyl caproate in the esterifying solution could reach 0.121%, while after adding 10% by volume yellow water to the esterifying enzyme solution, the volume fraction of ethyl caproate and ethyl lactate could reach 0.055% and 0.032%, respectively. The results is intended to provided a reference for the study of yellow water resources for Baijiu flavor enhancement.