Real-time hybrid testing technique (RT-HYTT) is a structural dynamic testing method that the numerical calculation of the equations of motion of a structure and the experimental measurement of the reaction forces resulting from the application of this motion to the numerical structure are simultaneously implemented in real time. In this paper, structural control performance of the magneto-rheological (MR) damper installed in a real-scaled 5 story building is experimentally evaluated through real-time hybrid test method. In this method, a numerical substructure is based on a structural model identified from the forced vibration testing results of a real-story building, and an MR damper that is used as an experimental substructure is physically tested with a universal testing machine (UTM). In the test, load cell on the UTM measure the force necessary to attain the required story displacement and these structural reaction forces are returned to the computer for use in next time step calculation of a numerical structural model. Test results show that the higher level of control force generated by the Mr damper causes the lower level of controlled response of a structure.