Abstract: Joint Russian-Chinese satellite-to-satellite Martian radio occultation experiment will be used to sound Martian ionosphere to derive electron density profiles. Compared with satellite-to-Earth radio occultation technique, satellite-to-satellite radio occultation technique has the better ability to receive higher signal-to-noise ratio radio signal and acquire more accurate profiles in a wider range (especially in areas of solar zenith angle of less than 43° and angle of larger than 138°. Joint Russian-Chinese satellite-to-satellite Martian radio occultation experiment is based on measurement of frequency shift between two radio signals penetrated the Martian ionosphere. The two coherent signals are irradiated from the transmitters. The frequencies of the signals are near 416.5 MHz and 833 MHz. The transmitters will be installed on Russian spacecraft Phobos-Grunt (FGSC) and the receivers will be installed on Chinese satellite YH-1. The relative frequency shift between two signals will reflect the property of Martian ionosphere.