Abstract: This paper studies on the failure mode and the hysteretic characteristics of the key steel underpinning truss-STCC joint，which lies in the large-span roof of Hohhot East Railway Station，by constructing a mixed-scales finite element model． It is explored the feasibility of using Drucker-Prager Cap material model in concrete hysteretic analysis． And it is constructed the joint model based on it to discuss the mechanical property differences of the joint model with and without filled concrete and the impact of the grade of the concrete． Also it is studied the mechanical differences between adopting internal stiffened method and local strength method combined procedures mechanical property of complicated joint in order to present some advices for structure design．