Abstract: Geometrical model of hydrostatic dry gas seal with different orifice cross-section shape was established. The transient flow field and pressure field of hydrostatic dry gas seals with orifice-type restrictor were solved numerically by large eddy simulation method. The steady-state performance, such as opening force and leakage rate, and pressure fluctuation characteristics adjacent to the outlet of orifice of hydrostatic dry gas seal with filleted or chamfered orifices and typical orifice-type restrictor were compared and analyzed. For the purpose of obtaining large opening force and small pressure fluctuation, the preferred values of chamfer and fillet were obtained. The results show that the fillet and chamfer on the outlet of orifice can enhance opening force and reduce pressure fluctuation of hydrostatic dry gas seal significantly compared to that with typical orifice-type restrictor. The preferred chamfer was from 0.3 to 0.4 mm, and the preferred fillet was from 0.1 to 0.3 mm.