The design of very low earth orbit satellites requires accurate and rapid prediction of aerodynamic drag in the free molecular flow region. Among the existing methods, the Test-Particle Monte Carlo (TPMC) method is more efficient, and can consider shadowing effect and multiple reflection effect, and is suitable for complex geometric shapes. In this paper, a new implementation of the TPMC method is proposed, which simplifies the calculation of initial velocity of test particles, and the method is applied to predict free molecular aerodynamic characteristics of Very Low Earth Orbit (VLEO) satellites. The results show that the TPMC method can give the aerodynamic characteristics of free molecular flow of the VLEO satellite quickly and accurately. The TPMC results are consistent with the Direct Simulation Monte Carlo (DSMC) results, which cannot be achieved by the panel methods.