In order to verify the validity of extended objects tracking algorithm under high precision sensors measurement, it is often necessary to compare with other algorithms and evaluate its estimated performance. Unlike classical point objects, the main task of extended objects tracking is not only to estimate the motion state of the objects, but also more importantly to accurately estimate their shape. As a result, there is an urgent need to the shape estimation performance evaluation of the extended objects. Aiming at the two kinds of representative extended target models based on star-convex and support functions, considering their different morphological parameters, an improved Hausdorff distance with different mathematical forms is proposed. Simulation results demonstrate that the modified Hausdorff distance can be used as an effective metrics to evaluate the shape estimation performance of the extended targets effectively.