Abstract: The mechanical properties of unequal angle cross bracing of ultra-high voltage (UHV) transmission tower were studied． Two full-scale internodes adopting unequal angle cross bracing，used commonly in UHV trans- mission tower in China，were made and carried on the static test under different working conditions． The strain de- velopment，the characteristics of deformation，the failure mode and the ultimate bearing capacity of the unequal angle cross bracing were mainly studied; then the nonlinear finite element analytical (FEA) model of internodes were established and verified by test． The parameters of FEA model of internodes were analyzed． The test results show that the bearing capacity of unequal angle cross bracing is good in different working conditions loading，when the load reaches the limit value，the failure mode of the unequal angle cross bracing was determined by loading mode to be out-of-plane buckling or out-of-plane and in-plane buckling． The parameter analysis shows that the bearing capacity of cross bracing is improved with the decrease of the internal force ratio，the increase of material strength and the increase of the intersection position． The improvement of bearing capacity of cross bracing is sig- nificantly affected by loading mode． Finally，based on the energy method and the finite element method，the theo- retical method of bearing capacity of unequal angle cross bracing were provided． It turns out that the theoretical re- sults are in good agreement with the results of test and FEA．

Key words: unequal angle, cross bracing, UHV transmission tower, bearing capacity, energy method, finite- element method