Abstract: Based on the direct simulation Monte Carlo (DSMC) method， the pumping performance of TMP (turbomolecular pump) blades in different rarefied gas flow regimes can be calculated. By changing the rotating speed， air inlet structure and the temperature of the pumped gas， the change of maximum pumping efficiency and maximum compression ratio of TMP can be obtained， and the influencing degree of each parameter on the performance of TMP in different flow regimes can be compared. At the same time， the change of the return flow of the turbine blades in different flow regimes is calculated. It is concluded that increasing the blade speed in the molecular flow regime can significantly improve the performance， and reducing the gas inlet area can improve the compression ratio of TMP， so as to provide the means to improve the performance and expand the working range of TMP.

Key words: TMP (turbomolecular pump), DSMC (direct simulation Moate Carlo) method, cross flow regime, pumping efficiency, compression ratio