Abstract: Post-construction assessment of beach restoration is an important approach to studying the effectiveness of beach nourishment projects and the stability of restored beaches. However, existing post-construction evaluations of beach stability in China predominantly rely on management assessments, and lack quantitative analysis of restoration mechanisms and structural efficiency, which hinders effective feedback for beach restoration research. Therefore, this study developed a refined post-assessment methodology, grounded in repeated monitoring, using numerical simulations of costal dynamic processes as the core and quantifying structural performance as the objective; a case study was also conducted at Weihai Beiliukou Beach. The results indicate that after restoration, the beach exhibited an evolutionary trend of “erosion in the east, stability in the center, and deposition in the west and wave-induced longshore currents were the primary driver of sediment transport and the erosion–accretion distribution. Auxiliary structures were well adapted to the regional sedimentary dynamic environment and significantly enhanced overall beach stability. The groins reduced sediment loss by approximately 11 000 m³/year. The submerged breakwaters achieved a significant wave height decrement rate of about 30% and reduced longshore sediment transport by over 60% in the sheltered area, and reversed the cross-shore sediment transport from an offshore transport of 13.7 m³/d to an onshore transport of 12.8 m³/d, reflecting the effectiveness and scientific basis of the restoration project. This shows that the post-assessment technical framework established in this study, which focuses on analyzing of sediment dynamic mechanisms and quantifying of structural unit efficacy, can provide methodological support for systematic and scientific post-construction evaluation.