Abstract This paper presents a numerical scheme that directly calculates the permeability field of the preform during the Resin Transfer Molding (RTM) process. The measured filling front locations as well as the corresponding inlet conditions are used in the proposed scheme to calculate the permeability field. The proposed scheme employs a numerical optimization algorithm to minimize a cost function that leads to the permeability filed of the preform. A time step independent RTM filling algorithm is utilized as a computational kernel to generate the cost function for the subsequent iterative minimization. The proposed permeability identification scheme is applied to test problems that involve isotropic and anisotropic permeability distribution within the perform. The results from these test problems verify the applicability of the proposed scheme.