Abstract. With the rapid development of satellite astronomy technique, In order to ensure the effective operation of the spacecraft in orbit, the spacecraft requires full ground physical simulation tests. So the construction of the ground simulation test system is an important guarantee for the development of space technology [1]. In the system of full physical simulation test for lunar orbit rendezvous and docking, the large supportive stage with super smooth surface is one of the most important large-scale precision test equipment, this stage can provide a high precision horizontal support surface in the range of 40m*30m for the test load, Each test load is usually supported by three circular air cushion, whose diameter is 200mm~400mm. High pressure gas is stored in the load equipment, and is released into the air through the air holes on the air cushion, A thin layer of air film is formed between the air cushion and the stage, the thickness of gas film is 10μm~15μm, The load equipment can freely move on the surface of a large stage with the gas film. There are strict requirements for the deformation of the system, Since the floating height is 10 μm and the test load is 3T. So the altitude difference of neighboring platforms is in range of 10μm. In order to guarantee the experiment effects, the paper analyses mechanical properties of the stage, distribute index of 10μm, and provide theoretical support for subsystem [2], [3].