The backcalculation of pavement layer moduli for layered system is researched with JILS FWD according to the model of 3 layered BP neural network and the theory of elastic layered system.The backcalculating ability of accurate network and noise network is compared through the backcalculation of theoretical and measured deflection basins. The key techniques are presented for the backcalculation of moduli with artificial neural networks.The comparisions of the noise network to the common backcalculation programs show that the backcalculation results for the method of neu...