Abstract: The stage separation of tandem layout vehicle is a complicated problem,including shock interaction,flow separation,vortices,and so on.The phenomenon has a great effect on the aerodynamic characteristics and trajectory of the first and the second stage.The study of the stage separation between stages of tandem layout vehicle is indispensable.This paper analyses the aero-dynamic characteristics and flow mechanism of stage separation without j et by the wind tunnel test.The tests are conducted in the FD-06 Sub-Tran-Supersonic wind tunnel in CAAA.The test model is a two stages model with tandem layout,connected to a stage separation support system, the distance and angle between stages are variable in this system.The aerodynamic characteristics of the first and the second stage are obtained by two six-component strain-gauged balances.The aerodynamic characteristics of the first and the second stage are analysed at typical mach numbers when the two stages are in-line.The test results of the second stage and the first stage at Mach number 0.75 and 1.79 are obtained.The results indicate that the two stages interfere each other in the stage distance range of the test condition (L/D≤2 ).As for the second stage,the axial force coefficient(CA)is related to the stage distance,the base drag coefficient(CAB)is negative as a result of “afterbody effect”which is a CFD result of a simple tandem layout,there is low speed vortex flow between two stages,and this phenomenon has a good effect on the separation of the two stages.The normal force coefficient(CN)and the pitch moment coefficient (MZ)of the sec-ond stage is not affected by the stage distance.As for the first stage at different mach number, the forebody axial force coefficient(CAF),CN and MZ are all affected by the stage distance,espe-cially at large angles of attack,where is shaking off the effect of afterbody flow of the second stage,the value of these aerodynamic coefficients increase with the increase of stage distance.