For the issue of the attenuation mechanism of skid resistance in asphalt pavements under water-accumulated conditions, a systematic study on the synergistic effects of water film lubrication and interface roughness was conducted using a self-developed water-environment friction testing system combined with an improved spring-slider numerical model. AC-13 dense-graded asphalt concrete specimens and styrene-butadiene rubber sliders were employed as experimental materials. Multi-condition friction tests were performed under fully submerged conditions, with high-precision strain sensors (resolution: 0.1 mN) used to collect real-time friction force-time curves, and buoyancy compensation technology applied to eliminate medium interference. Experimental results demonstrated that the presence of a water film reduced the average friction coefficient of the asphalt pavement compared to dry conditions, with stick-slip vibration amplitude decreasing by over 40%, confirming that the water film exhibits dual effects of lubrication and dynamic stability suppression. Further research revealed a nonlinear positive correlation between interface roughness and friction force: when Roughness (Ra) increased from 1.94 μm to 2.62 μm, the friction force rose by 14.7%, and under high roughness conditions, stick-slip amplitude increased by 28%. Under fully submerged conditions, cyclic loading reveals distinct stages in wear evolution: the first 1–3 cycles exhibit rapid degradation, transitioning to a steady-state regime. Based on a discretized multi-scale modeling approach, an improved spring-slider numerical model was developed. By introducing Gaussian-distributed interface spring strength parameters, the experimental phenomena were successfully simulated. The numerical results showed good consistency with measured data, with relative errors controlled within 5%.