Shear studs are critical important connectors in steel and concrete composite structures, and they will subjected to longitudinal shear force and transverse shear force, and as well as the tensile force under the applied loads. The mechanical behaviors of the studs are very complicated. In this paper, the spatial finite element model of Xinshiji Bridge, a steel truss arch bridge, was established, and the mechanical responses of the studs under various load cased were analyzed. The calculation results show that the shear forces of the studs under the dead loads are very small due to the structural characteristics of the bridge and the construction sequence of the bridge decks. Thermal effects, especially the effect due to temperature difference, are the key factors for the design of the studs in region near the ends of the bridge decks.