A combined process of organic acid-catalyzed hydrothermal pretreatment and alkali-assisted hydrothermal carbonization (HTC) is employed in this study to enhance the high-value utilization of vinegar residue, a by-product of the brewing industry. The effects of temperature, acid concentration, and reaction time on xylan degradation and the yield of xylooligosaccharides (XOS) were examined. With increasing reaction intensity, XOS yield exhibited a trend of initial increase, followed by decrease. Use of response surface methodology revealed that the optimal conditions were 82.5 ℃, 4.7% acid concentration, and 3 h reaction time. Under these conditions, XOS yield reached 22.28%, while the obtained products exhibited a low degree of polymerization and high purity. The overall retention rate of amino acids during the hydrolysis process under the optimal conditions was 61.42%. Subsequently, HTC treatment under 0.9 mol•L−1 alkali concentration, 200 ℃ and 13 h was conducted, reaching 21.78% and 45.84% yealds of humic-like acid (HLA) and fulvic-like acid (FLA), respectively, with a hydrochar yield of 13.92%. Structural analysis indicated that HLA possessed higher aliphatic content and longer side chains compared with commercial humic acid, whereas hydrochar exhibited a compact, ordered, layered structure. In summary, this process achieved the multi-component, high-value, synergistic utilization of vinegar residue, improved resource efficiency, and reduced environmental risks, thus laying a solid technical foundation for the resource utilization and functional material development of brewing by-products.