Abstract: High precision sandwich reflector panels of compact antenna test range are made of aluminum face sheet and honeycomb core treated by a special process. The constitutive parameters of this kind of sandwich panel are difficult to obtain by the traditional analytical methods and mechanical property tests. A mixed numerical-experimental model method was proposed to estimate the panel's equivalent elastic material parameters. In this method , the forward analysis was predicted using the finite element method and the inverse analysis was an algorithm combined genetic algorithm and gradient method. By using the proposed optimization algorithm and seamless integration between forward and inverse analyses , the mixed numerical-experimental model method was more efficient . A comparison between the results of numerical simulation and the experiment shows that material parameters from inverse identification describe the constitutive relations of this kind of sandwich panel faithfully. The numerical simulation model based on the parameters is reliable.