Abstract: In order to study motion characteristics of the separation between major and booster stages (stage separation) in thick aerosphere for supersonic tandem layout vehicle, wind tunnel free-flight test, with unrestrained motion freedom, was conducted. The kinetic law of relative display between stages was obtained for a supersonic tandem layout vehicle with or without residuary force of the booster stage at different initial separate angles of attack (AOA). The dynamic motion of the stage separation was observed in the experiment. The experimental conditions were Mach number Ma=2.5, the initial separate AOAs α=0° and 5°, and the angle of sideslip β=0°, respectively. It has been shown that:(1) The initial separate AOA has significant effect on the motion characteristics regarding the stage separation of the supersonic vehicle, and it is a pivotal parameter for the stage separation. The motion characteristics of the stage separation can be greatly improved by increasing the initial separate AOA. (2) The booster stage with or without residuary force has a trivial effect on the relative display. This behavior shows that the motion characteristics of the stage separation of the supersonic tandem layout vehicle are determined by the aerodynamic force exerted on the major and booster stage.