Abstract: Stage separation trajectory capturing test technique in the FL-23 wind tunnel was developed for investigating the stage separation dynamics of future multi-stage launch vehicle systems. By making use of the tunnel's upper and lower attack angle support mechanism and modification of servo-motors, transmission mechanism and control modules, a upper rig with two degrees of freedom of alpha, x, a lower rig with three degrees of freedom of alpha, x and y, and a coupling motion control system were set up. For a two stage vehicle, the two stage models and their force balances could be mounted on the upper and lower rigs respectively, and the stage separation trajectory could be simulated in the wind tunnel under control of the stage separation test computer, with coordinated motion of the angle of attack of the fore stage model, the angle of attack of the aft stage model, and the relative position in x and y directions of the two stage models. Conclusions could be obtained from verification experiments and client experiments, namely, the upper driving mechanism of the stage separation test system could pitch from –15° to 15°, and move from 0 to 200 mm in the x direction. The lower driving mechanism could pitch from –11° to 49°, and move from 0 to 680 mm in the x direction and from 0 to 507 mm in y direction. And the system could be used to conduct the tests for force measurement, model injection experiment, grid force measurement and capture trajectory simulation.