Ala-Lys-Arg-Ala (AKRA) is a non-volatile component in Chinese Baijiu, however, its taste characteristics have not been previously reported. This study aimed to investigate the taste properties of AKRA in ethanol-water systems and how they are affected by ethanol concentrations. The taste of AKRA was assessed using a combination of sensory evaluation and quantitative descriptive analysis, and its taste thresholds determined via taste dilution analysis. Then, the active sites of AKRA and its interaction with the sour taste receptor, PKD2L1, were explored through density functional theory, molecular docking, and molecular dynamics simulations. Results indicated that AKRA exhibited a sour taste both in water and ethanol solutions of varying concentrations (38%, 46%, and 54%), with taste thresholds increasing as the ethanol concentration increased, which were 0.28, 3.91, 7.73, and 16.42 mg•mL−1, respectively. The interaction between PKD2L1 and AKRA was dependent on hydrogen bonding and electrostatic forces, in which the key interaction sites included specific amino acid residues, such as SER264, SER30, and SER257. Although the increase in ethanol concentration theoretically led to an increase in the binding free energy between PKD2L1 and AKRA, with the absolute value rising from −25.620 kJ•mol−1 to −50.604 kJ•mol−1, the actual perception of the sour taste of AKRA decreased. Therefore, perception of the sour taste from AKRA was significantly affected by ethanol concentrations. Overall, the mechanism by which AKRA interacts with PKD2L1 involves hydrogen bonding and electrostatic forces, and an increase in ethanol concentration diminishes perception sensitivity to AKRA. This study provides a novel perspective for the study and modulation of flavor in alcoholic beverages.