To address reflective cracking and arching issues in road surfaces in Xinjiang, an investigation was conducted on the gradation design methodology and road performance characteristics of an oversized cement-treated gravel base (LCGB-50). Using the stepwise filling method and the variable-i (passing percentage decreasing coefficient) approach, the optimal coarse-to-fine aggregate ratio was selected based on 7-day mechanical strength, and a reasonable gradation range was determined for skeleton-dense cement-stabilised gravel with oversized particles. The dry compacted coarse aggregate porosity (VCA_DRF) method was applied for computational validation of the gradation design. The mechanical performance and frost resistance of LCGB-50 were verified through long-term strength tests and freeze-thaw cycle experiments. Finally, the serviceability of the material was evaluated using data collected from field trial sections and long-term environmental monitoring points. The results indicate that when the i-value is set to 0.70 with a coarse-to-fine aggregate ratio of 60∶40, the 7-day unconfined compressive strength and splitting tensile strength reach optimal values of 9.78 MPa and 0.91 MPa, respectively. The VCA_DRF test results show an error margin within 5%, confirming that a strongly interlocked, skeleton-dense structure is formed in the cement-stabilised gravel. Cores extracted from test sections remain intact, with 7-day compressive strengths exceeding 8 MPa, thereby meeting the design strength requirements and demonstrating high strength and uniform compaction. Monitoring data reveals that within a temperature range of -20 ℃ to 40 ℃, LCGB-50 exhibits superior strain recovery capability, which is 14% higher than that of conventional gradation sections. The occurrence of reflective cracking is reduced by approximately 57%. These findings demonstrate that the coarse-graded cement-stabilised gravel base possesses enhanced adaptability to temperature and stress variations, with reduced deformation fluctuation, indicating a clear performance advantage in mitigating the development of reflective cracking.