Abstract: The prefered ‘strong column-weak beam’ mechanism is not oberseved in most buildings in 5.12 Wenchuan Earthquake. The ‘strong column-weak beam’ design method in Chinses code are reviewed. Referring to international seismic design codes and related literatures, it is found that the damage pattern is affected by the following factors: the ratio of column-to-beam strength, over-reinforcement in the beam, contributions of the cast-in-site concrete slabs, scattering of material strength. Nonlinear dynamic analysis of RC moment-resisting frames excited by 20 strong ground motions are carried out to study the required ratio of column-to-beam strength and its heigh-wise distribution. It is found the required ratio of column-to-beam strength increases with the increase of earthquake intensities. Finally, some suggestions are given to ensure the realization of ‘strong column-weak beam’ mechanism.