Abstract: A numerical simulation approach is presented to simulate the rarefied two phase flow by applying two-way coupling technique in DSMC method. The interaction between the rarefied gas and solid particles is dealt with in a decoupled way to compute the momentum and energy exchange between phases. A numerical study of nano-particle following features for NPLS measurement technique used in the hypersonic wind tunnel is carried out by employing the DSMC method suited to simulate the rarefied two phase flow. The 50nm TiO₂ particles in various rarefaction two phase flow cases are simulated. The results show that nano-particle following features are satisfactory in the low rarefaction flow. As the degree of the flow rarefaction rises, the following features decrease deteriorate the difference between particle and gas distributions increase, and therefore the flow structure can't be obtained from NPLS correctly.