Abstract: Based on the relationship among axial force-bending moment-curvature on the section of the reinforced concrete member, a nonlinear finite element method considering P- effect and shear deformation of the member as well as analyzing the ultimate state of the frame is established. Thusly, an improved capacity spectrum method is put forward, the unique ductility factor of concrete frame is defined and the point of ultimate state in Pushover curve is determined as the demand point. On the condition that the demand point locates at the inelastic demand spectrum curve reduced by ductility factor, the maximum seismic spectrum acceleration is obtained to evaluate the seismic behavior of the frame. By balancing load carrying capacity, it’s concluded that the frames with 0.25―0.35 relative depth of compressive zone and 0.6―0.8 axial compressive ratios perform good seismic behavior.