Transmission towers have attracted more and more attention

for the phenomenon of their collapse existing widely in natural disasters.So it is significant to monitor the healthy condition of transmission towers.This paper introduces the expression of element modal strain damage index（EMSDI） in the field of damage identification

and further applies it into the model test of a transimission tower.The element shape function takes the place of the original calculation mehod of modal curvature

which effectively decreases the error in computing element modal strain energy and increases the accuracy of damage identification.In both the transimission tower numerical simulation and experiment

the validity and reliablity of this damage detection method are verified.The test case shows that the difference of EMSDI can exactly find the damage location and reflect damage extent in some degree.It can be used in damage identification of transmission towers.