To investigate the influence of aggregate size on the dynamic characteristics of hydraulic asphalt concrete, the effects of maximum aggregate diameters (19 mm and 37.5 mm) was focused on. Dynamic triaxial tests were conducted on hydraulic asphalt concrete with maximum aggregate sizes of 19 mm and 37.5 mm under identical mix proportion parameters. The equivalent linear viscoelastic model was employed to analyze the impacts of maximum aggregate size on dynamic stress-strain curves, dynamic modulus, damping ratio, and dynamic characteristic parameters. The hysteresis loops were modified based on the stress-strain behavior of hydraulic asphalt concrete. The results show that hydraulic asphalt concrete exhibits nonlinearity, hysteresis, and strain accumulation under cyclic dynamic loading. Under identical mix proportions and dynamic stress conditions, compared to conventional-sized aggregates (D_max = 19 mm), the dynamic strain of large-sized aggregates (D_max = 37.5 mm) increases by 43.1% at consolidation ratio K_c = 1.5 and 31.1% at K_c = 2.0. The damping ratio is relatively enhanced by 13.6%. The findings indicate that hydraulic asphalt concrete with large-sized aggregates (D_max = 37.5 mm) demonstrates superior deformation adaptability and seismic performance compared to conventional-sized aggregates. This study provides a theoretical basis for promoting the application of large-sized aggregates in hydraulic asphalt concrete engineering.