Abstract: To investigate the short-term mechanical enhancement mechanism of rice husk biochar (RHB)-cement synergistically stabilized road recycled aggregates (RRA), a RHB-cement co-stabilized RRA composite material was developed. The influence of RHB content (0%, 3%, 6%, 9%, and 12%) on mechanical propertieswassystematically studied through unconfined compressive strength tests, triaxial tests, SEM analysis, and XRD analysis, with a fixed cement content of 5% and 7-day curing period. The results indicate that RHB significantly improves the mechanical properties of the specimen, and unconfined compressive strength and elastic modulus reach 2508 kPa and 99 MPa, respectively, which are 59% and 23% higher than those of the control group. The 5% cement+6% RHB composite mixture can effectively replace the conventional 7% cement system, with its mechanical strength meeting the specification requirements for subbase layers of secondary highways. The RHB treatment increases the internal friction angleof specimens by 1%-3% and the softening characteristics are significantly enhanced, and the peak deviator stress and cohesion reach the maximum value at 6% dosage, and the peak deviator stress shows an increase of 33%-56% and the cohesion exhibits a 32% enhancement under different confining pressures. Based on the experimental results, an empirical formula for predicting the peakdeviatoric stress isdeveloped, and a mathematical model relating it to the unconfined compressive strength and confining pressureisdeveloped. Microstructural analysis reveals that RHB synergistically enhances mechanical properties through pozzolanic reactions and pore-filling effects. The research results establish an important theoretical foundation for promoting the engineering application of RRA in solid waste resource utilization.