A Complete Parameters Extraction Algorithm (CPEA) is proposed to improve the performance of Electrical Impedance Scanning Imaging (EISI). CPEA includes two parts: modeling of a forward problem and a parameters extraction process. The modeling of the forward problem is based an electrostatic scattering theory. With the model, we present an analytical solution of the forward problem. The solution process of the forward problem can be done in a very short period compared with conventional methods using iteration process. Based on the proposed model of forward problem, parameters extraction process could be regarded as a constrained optimization problem which is solved by a modified simplex optimization algorithm. Simulation experiments show that CPEA method can not only achieve more information of cancerous lesion within breast but also be more accurate and robust compared with other information extraction algorithms.