Lots of elementary and secondary school buildings were damaged by the devastating 921 Chi-Chi earthquake, so scholars proposed retrofit methods for increasing the seismic performance of school buildings, and the retrofit method by RC wing wall at columns can increase ductility and strength of buildings. After retrofitting by wing wall, the simplified pushover analysis can be done to understand the behavior of the structure. The simplified pushover analysis methods used to analysis the structure in this thesis are conventional simplified pushover analysis, slope-deflection pushover and software ETABS. Slope-deflection pushover is based on slope-deflection method with some assumptions. It is not only suitable for weak-column-strong-beam buildings but also strong-column-weak-beam buildings. Compared with experimental result, conventional simplified pushover analysis overestimates the strength and stiffness of the weak-column-strong-beam building. The strength, stiffness and ductility of ETABS analysis and slope-deflection pushover are conservative.