Mars exploration is one of the most important major deep space exploration projects. Some problems, such as navigation accuracyandsignal real-time transmission, exist in radio navigation because of the communication latency and occlusion of celestial bodies. Autonomous optical navigation is a key technology for mars exploration and could act as an important auxiliary for radio navigation. This paper focuses on the scheme and key technologies for autonomous optical navigation in mars exploration durling the cruise and capture phase. Firstly, some concept and scheme of autonomous optical navigation have been discussed, in which the optical navigation measurement model has been introduced for defining the relationship between celestialandoptical navigation camera, and the navigation scheme for marsexploration in cruise and capture phase has been formulated too. Secondly, some key technologies focusing on navigation image processing, on-orbit calibration for optical navigation camera and optical autonomous navigation filter design have been fully presented. In further research, these key technologies could take the advantage of the theoretical basis of Deep-space Photogrammetry.