The mechanical properties of the axial compression members of the double-shear splicing main members were studied through 10 sets of axial compression tests. The effects of different bolt connection lengths （120 mm， 180 mm and 240mm） and steel-clad area ratios （1.08， 1.22 and 1.31） were investigated. The ultimate failure mode， ultimate bearing capacity and load-displacement curve of the test members were compared and analyzed. The experimental results show that the ultimate failure mode of the angle steel main members without splicing joints is the flexural-torsional buckling failure around the main axis at the mid-span section， and the out-of-plane deformation is the largest and the torsional deformation is small. When the angle steel main member adopts the double-shear splicing joint， the axial compression ultimate failure mode is divided into two cases： when the bolt connection length at the double-shear splicing joint is not more than 120 mm or the steel-clad area ratio is 1.08， the compression failure mode of the main member is mainly mid-span cross-section flexural-torsional buckling， accompanied by the failure of the splicing joint. When the bolt connection length is greater than 120 mm and steel-clad area ratio is greater than 1.08， the compression failure mode of the splicing main member is the coupling failure of the flexural-torsional buckling at the mid-span near the joint and the local buckling at the inclined member. Combined with the test results， the existing calculation methods of the standards are demonstrated and analyzed， and the structural design suggestions of L125×10 angle steel main member are given. The research conclusions are conducive to promoting the development of transmission line structure design technology and laying a technical foundation for the compilation and improvement of transmission line structure design specifications.