As a main parameter of magnetotelluric sounding, the impedance phase has strong capability of resisting disturbance and high resolution in comparison with apparent resistivity. In this paper, through analyzing the relationship between the apparent resistivity and the impedance phase,the authors derived the recursive formula of phase apparent resistivity and analyzed the important properties of the impedance phase. With the processing and interpretation of magnetotelluric sounding profiles data measured in Yin'e basin as an example, the authors used phase recursive apparent resistivity and corrected the distortion of the apparent resistivity curve in the low frequency. It is shown that the apparent resistivity residual static effects have been better suppressed. Using the extreme point of the phase curve, the authors accurately determined the low-impedance Cretaceous layer interface, made up the inadequacy of the apparent resistivity data in interpretation, and described the application for impedance phase in the magnetotelluric sounding data processing and interpretation.