Abstract: Experimental study and numerical analysis on the aseismic behaviors of steel MRF including opening in beam web are carried out. Experimental results show that steel MRF including opening in beam web closed to connection can satisfy the design requirement. In the action of serve earthquake, Vierendeel-girder mechanism is formed in the weakened area, and the seismic energy is dissipated by local deformation of beam. The failure mode of steel MRF including opening in beam web is in conformity with the requirements of a ductile frame, i.e., “strong column-weak beam, strong connection-weak component”. A 17-story steel MRF building damaged during the Northridge earthquake is taken as an example to investigate the aseismic behaviors of steel MRF including opening in beam web. Analysis results show that with appearance of opening in beam web, the rigid of steel MRF is not weakened, and the failure mode of a ductile frame is formed. The maximum plastic zone moves to the weakened areas. Rotations around beam-to-column connection decrease and brittle weld fracture can be avoided. Aseismic behaviors of steel MRF is improved due to opening in beam web.