In system based seismic strengthening design, the redistribution of inner forces brought by the change of structural members can be considered, which is very important to guarantee the safety of a strengthened structure. Using SAP2000, the seismic behavior of a historic building was analyzed. After that, a system based seismic strengthening plan and a member based seismic strengthening plan were proposed. And the seismic behaviors of the building before and after strengthening were compared. The results show that the seismic behavior of the building can be improved with the system based seismic strengthening and the style and the feature of the building can be protected well.