The study presented in this paper verifies the seismic retrofitting effects of reinforcing over-track buildings with knee-brace dampers. Firstly shaking table tests were carried out on large-scale test models, to simulate over-track buildings reinforced with knee-brace dampers. Resulting responses or hysteresis loops, confirmed the seismic retrofitting effects of knee-brace dampers. In addition, natural frequencies and damping factors of the models were estimated by ARX model. Furthermore, analytical study of over-track building models simulating true structures confirmed the seismic retrofitting effects of knee-brace dampers.