As jumpers for overhead transmission lines increase In size, it Is necessary to take into the characteristics of jumper swaying space in order to determine jumper reinforcements adequately. From the theory of a structure made of beams, formulas for the sideway swaying of overhead transmission lines due to wind are modeled. And also natural frequency of the vibrated jumper is estimated to check the system resonance. The theoretical results can be led good suggestions to improve the economy and reliability of jumper structure.