Abstract: In microgravity simulations in the aerospace fields, the aerostatic thrust bearings affect the static and micro-vibration characteristics of the thrust bearings due to the addition of a time-varying exit boundary at the air film during the completion of the planar spanning-gap test, and the flow field inside the supporting air film varies with the change in the position of the time-varying exit boundary, thus affecting the static and micro-vibration characteristics of the thrust bearings. In order to clarify the service characteristics of aerostatic thrust bearings in the process of spanning the gap, the air film of aerostatic thrust bearings changes at any time when the change in the exit boundary of the macro-performance, this paper was based on the theory of hydrostatic gas lubrication, to build aerostatic thrust bearings planar spanning the gap of the laboratory bench, and carried out experimental research on the disc-type small-orifice throttling aerostatic thrust bearings with central air supply and three throttle orifices uniform distribution. The static and micro-vibration characteristics of bearings under different air supply pressures, different air film thicknesses, and different slot positions were analyzed. It was found that when the plane of the aerostatic thrust bearing spanned the gap, it was equivalent to adding a time-varying outlet boundary to the support air film. Moreover, there would be a high-pressure gas leakage phenomenon, which would lead to a reduction in the bearing capacity of the air bearing. When the throttle orifice faced the gap directly between the experimental tables, the self-excited micro-vibration amplitude of the bearing was the smallest. In the process of plane cross-seam of aerostatic bearing, under the same air film thickness, with the increase of air supply pressure, the static bearing capacity and static stiffness of the bearing were improved. With the load increasing, the micro-vibration amplitude of the air bearings with the throttle orifice directly above the splicing gap reduced.