In order to increase the structural longitudinal stiffness and facilitate the swing method, the side girders of trough section of the cable-stayed bridge on the Kunming-Shanghai passenger line were inserted into the pylon so as to form the pier-tower-girder fixed region. For the (32+80+112) m single tower cable-stayed bridge, the structure and force of the fixed region are very complicated. The large general-purpose finite element software ANSYS was used to establish the pier-tower-girder fixed region model to study the stress distribution of the fixed region. The correctness of this model was verified. Based on this region model, the force transmission and stress distribution of the fixed region were investigated, and the effect of the local structural details on the fixed region stress was studied. The analysis results show that the global stress level of the fixed region is lower than the girder and tower, but there are stress concentration phenomena in the fixed region, such as the intersection point between the floor of the trough girder and upper tower, and the corner of the human tunnel in the fixed region. The degree of the stress concentration was relieved significantly by improving the structural details.