Abstract: The Mars landing exploration mission is characterized by multiple task links, high complexity, and high environmental uncertainty, with a very low success rate of not more than 50%. China has just successfully completed her first Mars exploration mission with the Tianwen-1 Mars probe and the process of “circling, landing and roving” was completed all in one mission as the first such example in the world. This paper discusses the factors of Mars environment being considered in this Mars landing mission and the determination of quantified environmental conditions, including the requirements of each subsystem with respect to the environmental boundaries, the elements of the Mars space environment, the Mars atmospheric environment and the surface environment, focusing on the determination of the environmental factors that affect the enter, descent and landing process, and the determination of the deviation range of the environmental parameters. It is shown that with the above design considerations, important inputs and constrains can be provided for the control and the parachute opening in the landing process, thus, in a large extent, the success of the whole mission is guaranted.