Abstract: In this paper, first of all, the method to estimate the rotational components of ground motions is given according to the theory of elastic wave propation. And then, the system composed, of 60 KVtransmission tines and their supporting towers crossing the Hun river in Shenyang area is analyzed The equation of vibration for the tower-line coupting system is derived under the combined avtion of horizontal and rocking sersmic motions. By use of TCCV90 computer programme compited by the authors of this paper, xome results with practical singiflcance are obtained, referring to the systematic seisnuc resoinse abaktsis.