The adhesion performance at the bitumen-aggregate interface is a critical factor in mitigating pavement water damage, as it directly influences the service life of road infrastructure. To address the limitations of conventional modifiers, such as high costs and complex processing, low-molecular-weight polyolefin was employed as a modifier for bitumen mixtures in this research. By proposing a hierarchical research methodology that integrated microscopic wetting behavior, interfacial energy optimization, and macroscopic performance validation. This study overcomed the traditional single-scale limitations and achieved systematic innovation from microscopic mechanisms to macroscopic performance. A comprehensive approach combining contact angle measurements, surface energy analysis, and interfacial energy parameters (adhesion work, Was; spalling work, Wasw; energy ratio, ER) was utilized to investigate the effects of polyolefin dosage (2wt%~8wt%) on the interfacial interactions between bitumen and three lithological aggregates (granite, basalt, limestone). Multivariate regression analysis and modified boiling water tests were further conducted to validate the adhesion enhancement mechanisms. The experimental results demonstrated that low-molecular-weight polyolefin significantly reduced bitumen contact angles (8%~58%), thereby improving wettability and interfacial bonding. Was increased by 38.3% to 39.5%, ER increased by 1.38 to 1.41 times, and Wasw decreased to -94.86~-97.85 mJ/m2, collectively confirming enhanced interfacial stability. The optimal polyolefin dosage varied with aggregate lithology: granite, basalt, and limestone achieved the minimal Wasw values (-97.85, -96.15, and -94.86 mJ/m2) at dosages of 2wt%, 4wt%, and 6wt%, respectively. Correlation analysis revealed a strong positive relationship between polyolefin dosage and ER (correlation coefficient=0.90, p<0.01), which outweighs the influence of aggregate oxide composition and underscoring the dominant role of polyolefin in adhesion enhancement. Experimental validation showed a 34% reduction in the spalling rate (Wb) and a significant improvement in water stability. This research provides a theoretical foundation and technical support for the application of low-molecular-weight polyolefin in bitumen pavement engineering.