Abstract: For the issue of navigation during the interplanetary cruising, a celestial navigation based on the Sun and Planets observation is proposed. According to the position of a probe in solar system, Sun/Earth and Sun/Mars are selected as targets for navigation observing. Respectively, Sun sensor and optics navigation sensor on the probe are used to measure line of sight. The fundamental of the observation schemes is analyzed and the measurement equations are educed in details. The orbit parameters of the probe are estimated in real time by utilizing extended Kalman filter. Finally, the autonomous navigation methods presented are verified by the data of 2020 Mars mission. Simulation result shows that the estimation accuracy of position and velocity can meet the requirements of the interplanetary cruising phase.