A 2-D Type-Discriminated Geometric Theory of Diffraction based (TD-GTD) model that discriminates between the localized and distributed scattering centers of the radar target is presented. This scattering model provides a more physical-relevant and richer description of high frequency complex scattering behavior compared with either point scattering models or prony models. To estimate the TD-GTD model parameters, Maximum Likelihood Estimation (MLE) algorithm is developed. An effective method of parameter initialization is proposed. Since estimating parameters of all scattering centers at the same time is the cause of high computational cost and complexity, RELAX technique is introduced into MLE algorithms to get around that difficulty. The efficiency and feasibility of the method is confirmed by the test based on the measured data.