Abstract: Investigations of planetary atmospheres, ionospheres, rings, and magnetic fields using radio science techniques have been conducted by almost every planetary mission, and have acquired many significant scientific results. Changes in the frequency, phase, amplitude and polarization of spacecraft radio signals, caused by passage through a planet's atmosphere and ionosphere, have been observed in rising and descending planet occultation events. Utilizing an inversion method, we can obtain the refractivity profiles of the atmosphere, as well as the density, temperature and pressure profiles of the neutral atmosphere, and the electron density profile of the ionosphere. In the first Chinese YH-1 Mars mission, characteristics of the Martian atmosphere and ionosphere will be detected by a radio occultation experiment. The details are presented in this paper.