The physical meaning of the apparent resistivity ρ_zy which is defined by the ratio between magnetic field's components and its phase in the frequency electromagnetic sounding with the electric dipole sources is discussed and the method of estimating the phase by using the data of the apparent resistivities on the basis of dispersion relation is given. It has been proved that the estimated phase values coincide with those calculated by theoretical models. In addition, the ρ_zy-φ_zy joint inversion problem is studied and the practical software which has a better effect in the application is developed.