Nonlinear finite element (FE) analysis models of CFT composite frames with floor slab were established by Msc.Marc to investigate the seismic behavior of composite frames. A number of material nonlinearities and contact nonlinearities, as well as geometry nonlinearities, were taken into account, including elastoplastic properties of steel and concrete, concrete cracking and tension stiffening, steel fracture, interface slip between concrete slabs and steel beams, P-D effects etc. The elasto-plastic behavior, as well as fracture and post-fracture behavior, of the FE analysis models agreed well with those of the test specimens. The beam and panel zone deformation of the analysis models is also in good agreement with that of the test specimen. It is concluded that FE analysis is useful not only for monotonic load analysis but also for cyclic load analysis. It is a helpful tool to expand the information on seismic behavior of composite frame.