For landing on planet, a dual control strategy is developed to solve the problem of poor estimation performance which results from the lack of observability. The system uncertainty is incorporated into the quadratic performance index as a cost by extending state space, which takes advantage of the nonlinear coupling between observability and trajectory to overcome the lack of observability and to achieve better estimation performance. By stochastic optimizing the landing trajectory, the overall performance of GNC system for landing on planets is improved.