Adaptive　disturbance　rejection　filter　(ADRF)　approach,　an　active　vibration　control　for　flexible　spacecraft,　is　developed　and　its　parameters　are　identified　using　a　closed-loop　system　method.　Particularly,　semi-physical　experimental　study　of　a　maneuvering　spacecraft　equipped　with　a　flexible　manipulator　is　implemented　to　demonstrate　the　improvement　of　the　attitude　control　performance.　The　control　system　consists　of　two　main　parts:　(1)　optimal　input　shaper　is　applied　to　the　flexible　manipulator　to　suppress　the　vibration　and　alleviate　the　effect　of　the　vibration　on　the　spacecraft;　(2)　ADRF　is　presented　to　mitigate　the　equivalent　periodic　disturbance　caused　by　the　nonlinear　coupling　between　the　spacecraft　motion　and　the　manipulator　vibration.　The　disturbance　frequency　adaptation　tracks　the　frequency　of　the　periodic　disturbance　using　adaptive　notch　filter,　and　the　obtained　frequency　is　then　fed　to　disturbance　rejection　filter.　The　ADRF　approach　can　provide　optimal　sets　of　gains　based　on　the　characteristics　of　the　system.　The　semi-physical　experimental　results　show　that　the　frequency　tracking　method　works　quite　well　to　be　used　in　a　real-time　controller.　The　results　also　indicate　that　the　ADRF　can　provide　significant　vibration　reduction　and　improve　the　attitude　control　accuracy　of　the　spacecraft　body.