Abstract: A method for Martian atmospheric entry guidance is researched in this paper,regarding the problems faced by Mars exploration vehicle with low lift-to-drag ratios. Firstly,with a certain ballistic coefficient and lift-to-drag ratios,the initial reentry angle is designed considering the process variable constrains and the parachute deployment constrains. Then the reference trajectory is developed for providing the sufficient margin to overcome the parameter uncertainties considering the nonconforming terminal constrains and the low control authority. Finally, the tracking guidance law is presented. The six degree of freedom simulation demonstrates the effectiveness of the approach,which provides references to the Mars exploration project.