According to the characteristics of the hypersonic flow field in near space

the computational format of the mass equation of direct simulation Monte Carlo-information preserve (DSMC-IP) method was improved by the Van Leer scheme. The local Mach number was set as the standard of the flux splitting

and the transport fluxes on both sides of the cell interfaces were reconstructed. So the computational format has the characteristic of the flux splitting

and the application problems of the DSMC-IP method in hypersonic flow field were solved. The two-dimensional hypersonic flow field in near space was simulated by the improved flux splitting DSMC-IP method with unstructured grid. The solution of computation by the flux splitting DSMC-IP method has good agreement with the results of experiment and reference value

and the statistics dissipation of direct simulation Monte Carlo (DSMC) method was reduced significantly. When the flow becomes more rarefied

the non-equilibrium effect becomes more obvious. In this situation the results of flux splitting DSMC-IP method differs within 10% from the reference values

so the characteristic of the flow field is well reflected in non-equilibrium situation. The results prove the feasibility and validity of the flux splitting DSMC-IP method.