Abstract: The flat-shell element was constructed by the combination of plane stress element and thin plate bending element,it could be effectively used to analyze shear lag effect of short pier shear wall in the elastic stage proved by the low cyclic loading test. Test and finite element analysis showed that the normal stress distribution in the flange plate section was not even in the elastic stage,shear lag effect was obvious,normal stress concentration was easy to appear in the juncture of web and flange plate,normal stress distribution in the flange plate section was changed to more uneven and the maximum normal stress position was changed with the cyclic loading because of stress redistribution in the plastic stage. So,the flange plate section must keep space for stress redistribution to guarantee that the most part of the flange plate section can fully display the bearing capacity with the development of plastic deformation.