It is a study estimation of electrical resistivity distribution of subsoil was done through electromagnetic field measurements on Earth surface by means of magnetotelluric method.In general form, the task of electrical resistivity calculus implies the resolution of a direct problem which involves the calculation of electromagnetic fields on surface this supposes a pattern of flat soil in N layers which aids to resolve an inverse problem through which electromagnetic data seen on the surface are adopted theoretically to data predicted. The inverse problem is solved to do a language software of Matlab programme.