Abstract: In the main power house structures of the thermal power plant with SＲC frame -ＲC scattered shear wall ， there are plenty of abnormal joints between steel reinforced concrete column and reinforced concrete beam． These joints belong to the type of abnormal joints with cross-section mutation column，beams on either side of the column being not on the same level and staggered floor，and low-cycle reversed loading experiments were carried out for the abnormal joints to research their failure mechanism and mechanical behavior． The results indicate that the failure process of the joints experienced four stages of initial crack，entire crack，limited crack and failure． Finally，these joints were failed by the destruction of column end plastic hinge． Steel reinforced concrete structure members have better late deformation and bearing capacity than ordinary reinforced concrete structural members under strong earthquake． The stress mechanism of these abnormal joints could be explained by compression strut mode and steel truss mode．