Abstract: A flexible circular bolted flange joint with Q690 high strength steel used in 1000kV steel tube towers is constructed. In order to investigate the performance, the failure pattern of the bolted flange joint and the bolt force, axial tension tests and nonlinear finite element analysis have been carried out on two full-scale flange specimens. Both experimental and FEM analytical results show that the flange used in a 1000kV steel tube tower is safe, and has an adequate safety reserve. The weakest part of this joint is a connection location between a tube and a flange plate. It is recommended that the value of this flexible flange bolt load correction coefficient m should be 0.62, and the thickness of the tube should be taken accounted for calculating the ultimate bearing load.