Abstract: DSMC (Direct Simulation Monte-Carlo) method was utilized to simulate the flow field in a gas centrifuge from the point of view of the kinetic theory. The computational program was based on the improved G2 procedure, in which the radial weight factor was corrected. Relative to the original procedure, the improved program was suitable for simulating more complex flow fields and had higher computation efficiency. The results was consistent with the analytical solution of the isothermal rigid body rotation. The flow field with circulating flows in the gas centrifuge in the case of the wall thermal driven was obtained through fixing the temperature gradients on the wall boundary. The results suggested that DSMC method is capable of the simulations of complicated flow field in a gas centrifuge.