Asphalt concrete (AC) overlays placed over old asphalt pavement have become an altative to repairing and reinforcing pavements.The strength contributed by the AC overlay is strongly influenced by the anisotropic properties of the pavement material.This study was conducted to analyze the influence of anisotropy,modulus gradient properties,and the condition of the AC overlay and old pavement contact plane on the mechanical behaviors of AC overlays,as well as to quantify the influence of the degree of anisotropy on the mechanical behaviors of AC overlay by a sensitivity analysis (SA).The mechanical behaviors of the AC overlay were numerically obtained using the threedimensional finite element method with the aid of ABAQUS,a commercial program.Variations in the AC overlay’s modulus as a function of temperature as well as the contact state between the AC overlay and AC layer were considered.The SA is based on standardized regression coefficients method.Comparing the mechanical behavior in terms of surface deflection,stress,and strain of the anisotropy model against those corresponding to the isotropic model under static loads show that the anisotropic properties had greater effects on the mechanical behavior of the AC overlay.In addition,the maximum shear stress in the AC overlay was the most significant output parameter affected by the degree of anisotropy.Therefore,future research concing the reinforcement and repair of pavements should consider the anisotropic properties of the pavement materials.