Abstract: The ultimate strength of a dual-angle cross combined section of high-strength steel was researched based on experimental and theoretical analyses. The influence of slenderness ratios, limb-width ratios and filled plates on the strength was researched. According to thin-plate energy theory and a virtual work principle, the formula of ultimate strength was derived and the calculation method of ultimate strength was proposed and compared with that of normal coded one. The results show that the analysis model and proposed method had theoretical and practical significance for engineering design.