Abstract: The cause of instabilities in aerostatic bearing systems operated in a vacuum environment is studied in this paper. In order to eliminate this type of self-excited resonance, some pertinent remedies are suggested which can be used to maintain the ambient pressure of the bearing in a range of about 1±0.2 atm.. This will improve the performance of the instruments using aerostatic bearings as well as increase the percentage yield of qualified bearings.This work was done under the guidance of Prof, and Dr. T. C. Lin.