Abstract: Based on the upcoming self-Mars Exploration Program of China, the whole process of the optical auto-navi during the Mars exploration cruise segment is studied in this paper. Using the design orbit of the cruise section, the selection criteria and the asteroids sequence for optical navigation are given. The length of observation data arc is set to 30 days, and the period of the observation data is 5 days. Using the weighted least squares algorithm, the position error is from 100km to 400km and the velocity error is less than 0.25m/s when the length of observation data arc is 30 days.