To analyze the stress safety and shear force-transferring mechanism between steel and concrete in cable-stayed bridge with group aggregation anchor system, which is a new architecture of the cable-stayed bridge, a finite element model of anchorage zone was established by ABAQUS software based on an actual bridge project. The loading and boundary conditions of the sectional model were determined according to the equivalent beam element model. The stress distributions of the concrete pylon and steel box girder under three load cases were studied. According to the analysis of stress and displacement of the interface between concrete pylon and steel box girder, the force-transferring mechanical performances with different levels of pre-tension loss and friction coefficients were investigated deeply. The analysis results show that the shear force at the end of the steel girder is mainly undertaken by friction in design load case, indicating there is no relative sliding between the concrete pylon and steel box girder with enough safety margin. When the pre-tension loss reaches 60% or the friction coefficient of interface reduces to 0.2, the critical friction state is achieved and relative sliding is increased, which makes the structure unsafe.