This study deals with the identification of the complete set of mechanical parameters associated to elasticity, plasticity and failure of starch-zein composites. The approach is based on three-point bending experiments and a finite element (FE) simulation approach. FE simulation of three-point bending test is implemented using a simple elastoplastic model. The identification of the mechanical parameters is handled using all optimisation technique based on a error-gradient method. The purpose of the optimisation is to compute the set of mechanical parameters that makes the best match between the FE and the experimental results. In the first linear part of the force-deflection curve, a unique Young's modulus Value is predicted assuming isotropic behaviour for all studied samples. In the plasticity part, two quantities namely tangent modulus and yield stress are Suggested to describe the plasticity behaviour of the starchy composites. Failure possibility is assessed using maximum strain criterion, where failure probability distribution within the sample is computed. The predicted results show that the simple elastoplastic model is a realistic model to describe the mechanical behaviour of the starchy composite LIP to failure. Different distributions Of failure probability are predicted depending oil which strain component is used to assess the failure possibility