This study uses multivariate adaptive regression spline (MARS) for determination of maximum shear modulus (G max ) and minimum damping ratio (ξ min ) of synthetic reinforced soil. MARS employs confining pressure (σ, psi), rubber (r, %) and sand (s, %) as input variables. The outputs of the MARS are G max and ξ min . The developed MARS gives equations for determination of G max and ξ min . The results of MARS have been compared with the adaptive neuro-fuzzy inference system (ANFIS), multi-layer perception (MLP) and multiple regression analysis method (MRM). A sensitivity analysis has been also carried out to determine the effect of each input variable on G max and ξ min . This study shows that the developed MARS is a robust model for prediction of G max and ξ min .