Unbalanced tension load is defined as a load directed along the conductor, and its load scale greatly varies according to the conductor's supporting system, the span length between the towers, and the conductor's horizontal and vertical angle against the tower. Unbalanced tension load is an important factor which should be considered when designing Japanese transmission towers, which are typically constructed in mountainous areas. We then carried out non-linear stress analysis for wind loads on a transmission tower, assembled a record of strong winds resulting from recent typhoons that passed through Kyushu. As a result, it was revealed that a large unbalanced tension load was applied to the line; therefore, we studied to find an appropriate countermeasure for it.