Abstract: Aiming at precision landing of Mars entry for Mars exploration mission, this paper proposes a novel drag-based nonlinear predictive guidance law. Taking into account the aerodynamical parameters perturbation of Mars vehicle, the air density parameter perturbation of Mars, external disturbance and initial states errors, a nonlinear predictive guidance law based on optimization theory is designed for the three-dimensional Mars entry model. The simulation results indicate that under the proposed guidance law, the Mars vehicle achieves a precision landing with the control constraint being satisfied.