Based on the design of immersed tunnel of Shenzhen-Zhongshan Link, a refined nonlinear finite element model of immersed tunnel segment was built and a shear test was simulated. The results show that, in the transverse direction, the transverse steel diaphragm and the concrete bear the tension and compression, respectively, forming the main truss system. While in the longitudinal direction, no obvious lateral stress distribution is shown. The angle steel connectors mainly transfer the shear forces between steel and concrete, while the uplift forces are comparatively lower. At elastic stage, the shear stiffness of angle steel is close to each other and the shear force distributions are uniform. After the concrete near connectors cracking, the shear force undertaken by the structure is still increasing. In the whole shear process, the concrete cracks in bending area, the concrete cracks near the connectors, the yielding of transverse steel diaphragm, and the concrete diagonal cracks under shear occurred to the structure successively. The structure reaches the ultimate shear capacity with diagonal cracks, leading to the failure of the structure.