Mars Express, the first planetary mission being conducted by European Space Agency (ESA) has successfully launched in December 2003. MARSIS is a radar on board Mars Express (MEX) which probes the atmosphere of Mars when working in ionosonde mode. It provides ionograms from which information on the ionosphere can be derived. However, from the recorded signal to the physical parameters which are derived, there is a complex inversion problem which is dependent on the model of the refractive medium, and the present analysis mode does not use the richness of the data. The project which is proposed here deals with the development of a new analysis tool based on a new approach of the inverse problem. We want to develop a numerical model of the magnetized ionosphere which will be included in the new analysis tool. The inverse problem will not be tackled directly, but the feedback between the simulation of the refraction and the control parameter on the atmosphere and the ionosphere will allow deriving the parameters of interest.Thus, the project was proposed to develop an innovative analysis module which will be included to the processing tool for ionosonde data developed at ESTEC.This report first gives a general introduction of Martian atmosphere environment, ionosphere structure and sounding operation. Then the short description of Mars Express and instruments on board is presented. The steps of building the new model and its corresponding results are discussed in detail. The loops are tested and fitted with Viking data and MARSIS data which proved to be validity. Finally, the conclusion and future work direction are also explained in the last.