In performance-based seismic design method, it is very important to have a good command of the nonlinear performance of a structural system, including in the collapse stage. In this paper, a nonlinear finite-element analysis on reinforced concrete moment frames is carried out. After studying the forces and deformations behavior in beam-column elements, the element stiffness matrix of distributed plasticity beam-column element is deduced using the Cotes scheme with 5 integration points. During the occurrence and development of plastic hinges, sections at some integration points will experience loading, unloading and reverse loading and the stiffness of these sections will experience various status. A quadrilinear form moment-curvature relationships with curvature- softening behavior and the hysteretic modes are used in the nonlinear static analysis program. The numerical analysis is carried out and the numerical results validate the load-displacement relationships and the yield mechanism of experiment frames.