Abstract: The liquid propulsion system of the Mars Ascent Vehicle (MAV) provides orbital control thrust, as well as attitude control forces and torque, which is crucial for ensuring the MAV’s payload capacity, precise orbital insertion, and reduced energy requirements. The system undergoes complex mission profiles, including Earth-to-Mars transfer, Mars orbital insertions, Mars EDL (Entry, Descent, and Landing) flight, and storage on the Martine surface before being operational. This paper addresses the strict constraints on structural mass, envelope size, and available energy faced by the MAV’s liquid propulsion system. It systematically reviews key technologies required for lightweight, miniaturization, and high-precision orbit insertion, such as thrust, specific impulse, environmental adaptability and reliability. A design solution incorporating low-freezing-point propellants, medium-chamber-pressure engines, surface tension common-bottom tanks, and a highly reliable, highly integrated system is proposed. The results provide an important reference for the formulation of the Mars ascent vehicle’s design scheme.