The seismic design provisions of the 2005 KBC has been based on the 2000 IBC and has considered the building code situations in Korea. There are site ground motion, soil class, seismic design category in the significant changes of the 2005 KBC. In the case of soft soil condition, the response spectrum acceleration of the 2005 KBC is larger than that of previous code. To reduce the seismic force of the 2005 KBC, it need to introduce the eqrthauke force resisting system with high ductility.