Abstract: To quarantee the seismic behavior of adding frame steel structure and the integrity between adding structure andoriginal structure, the steel base joint is the key to the project of adding story. It is analysed the configurationof column basejoint of steel frame structure adding story when the original structure is a concrete frame structure, and it is pointed out theseismic inadequacy of the base joint used at present, and a new seismic constructional disposal of the joint of steel frameadding story on the top of a tall building is suggested.