Abstract: The transport system of two-stages-to-orbit (TSTO) has many advantages, such as easy to implement and much less expensive. Successful separation between the two stages is a critical issue to design a TSTO transport system. Compared to a regular concatenation configuration with the front and back in-line layout, there is serious shock interference between the two stages of the TSTO parallel configuration, which obviously changes the aerodynamic moment of stages and consequently affects the attitude of upper stage during the separation procedure, such as the pitch angle. In order to simulate the multiple reflections of the moving shock wave between two stages in the separation process, a parallel mesh dynamic optimization technique for the separation process is established by combining the unstructured hybrid mesh distribution optimization technique and the pressure ratio based shock wave identification technique. The whole separation procedure was numerically simulated using the general computational fluid dynamics (CFD) software NNW-FlowStar. The results show that with mesh adaptation techniques, the complicated shocks between the two stages can be precisely captured, the more accurate aerodynamic moment can be obtained by CFD and hence the prediction precision of the trajectory and attitude can be improved significantly.