Introduction  In order to explore the main control conditions of each member of the transmission tower, this paper calculates the 500kV double circuit tangent tower, summarizes and classifies all kinds of members, and identifies their control conditions, so as to provide reference for the future design of tangent tower.

  Method  This paper introduced the typical operating conditions in tower design. Taking the 500 kV tangent tower as an example, this paper identified the control forms of each member through calculation based on the hanging point load of the tower, and summarized the identification results to find the changes in the law.

  Result  For the hanging point, the operating condition with the maximum load in X direction is 90° strong wind, the operating condition with the maximum load in Y direction is broken line, and the operating condition with the maximum load in Z direction is lifting. The operating condition with the maximum total load is lifting. The normal operating condition controles most of the main members of the tower, and the 60° strong wind directly affects the foundation force. The broken line condition controls most of the cross members of the tower, and the installation condition controls the fewest members. Considerable members of the tower are controlled by the load out of the plane due to the same pressure. These members are mainly the cross members from the lower chord of the upper cross arm to the upper chord of the middle cross arm on the front of the tower, and the cross members below the variable slope, and attention should be paid to these members in the design.

  Conclusion  Tangent tower is featured by great numbe, various models and layout forms of members. In project construction, the members should be optimized according to the design conditions and the control conditions of members.