Abstract: Control of separated flow over civil aircraft aft-body and drag reduction mechanism by using vortex generator have been presented by means of wind tunnel force test, oil flow and PIV flow visualization test. It shows that the height, installation angle and fixed-location of vortex generator are the main parameters to separated flow over aft-body, while sweep angle and length of vortex generator have little effect. When vortex generator is installed at a negative attack angle, location near tail of fuselage proves energy-efficient to drag reduction. In a preferable control scheme of vortex generator, oil gather line in the separation area of aft-body is obviously deferred, and the separated eddy measured by PIV is obviously smaller, which validates the force test results.