This paper studied a one-dimensional model of high-vacuum plane circular gas-bearing with a three-stage sealing system, and analyzed the performances of the high-vacuum gas-bearing by combining the finite element method and the flow rate principle of the vacuum technology. For an expected pressure in the vacuum chamber, the zero load-capacity accident could take place. The reasons for the zero load-capacity accident were given through analyzing the flow rate of each sealing stage while the relationship between the pressure in the vacuum chamber and the inlet pressure was obtained. Besides, the influences of many parameters on the vacuum degree limit of the vacuum chamber were examined carefully. The analysis in this paper showed that for a given multi-stage seal system, the vacuum degree limit of the vacuum-chamber was inherent at the nonzero load-capacity condition.