Abstract: An adaptive iterative guidance strategy was designed for the guidance of Mars ascent vehicle in the orbiting phase. To reduce the effects of initial state deviation and the uncertainty of the Martian environment, the remaining flight time was calculated iteratively in the guidance coordinate system in each cycle, and the optimal control angle satisfying the constraints of the target point position and velocity vector was solved under the fixed thrust of the ascender, so as to correct the flight trajectory in real time. The simulation results show that compared with the traditional open-loop guidance scheme, the proposed scheme significantly improves guidance accuracy, in which the altitude error is reduced by three orders of magnitude, the maximum velocity error is reduced to one-third of that of the original open-loop guidance, the orbital inclination and eccentricity errors at the entry point satisfy the basic engineering requirements, and it can be used as a reliable scheme for the future guidance of the Mars ascent vehicle in the orbiting phase.