This study systematically evaluates the feasibility of incorporating coal gangue into highway subbase materials. Comprehensive mechanical tests, including unconfined compressive strength (UCS), bending tensile strength (BTS), dynamic compressive resilient modulus (DCRM), and microstructural analyses via X-ray diffraction (XRD) and scanning electron microscopy (SEM), were performed on cement-stabilized coal gangue-crushed stone mixture (CGM). A Multi-criteria Optimization and Compromise Solution (VIKOR) multi-criterion decision model, integrating Delphi-Entropy weighting, was developed to optimize selection based on mechanical performance, economic viability, and environmental impact. Results indicate that reducing coal gangue content improves mechanical properties across curing stages, with coarse aggregates (9.5 mm–31.5 mm) dominating strength development. Notably, 60 % and 40 % coal gangue mixtures showed 25.6 % and 22.5 % compressive strength increases from 28 to 90 days, surpassing conventional crushed stone mixtures (19.8 %). Failure mechanisms shifted from plastic compression failure at the interfacial transition zone to brittle fracture at weak interfaces under bending stress. Microstructural analysis confirmed delayed pozzolanic reactions enhanced late-stage strength, with optimal C-S-H gel and AFt crystalline networks in 40 % coal gangue mixtures. The VIKOR model identified T/4 and 40 % coal gangue formulations as optimal subbase materials, balancing mechanical performance (compressive strength: 5.2 MPa; bending strength: 1.1 MPa) with sustainability. This study provides a framework for eco-efficient infrastructure material design while promoting industrial byproduct valorization.