In this paper, a new algorithm for backcalculating pavement layer moduli from pavement deflection basin is presented. The algorithm uses SDUFEM finite element based backcalculation program in the iterative process and adopts backcalculating pavement layer moduli at fixed Poisson's ratios. After forward calculation for surface deflections at specific points is made with known elastic properties, flexible pavement layer moduli are backcalculated using new algorithm.