Abstract: To promote structural systems with replaceable components in the new urbanization process, connections with LYP160 steel cover-plate components in steel frame systems were improved by widening the beam flange section to increase the bearing capacity and fuse performance. A numerical model of full-bolted connections was established by using ABAQUS and was proven correct and applicable due to test results at home and abroad. Subsequently, cover-plate connection models with different degrees of widening and weakening of the flange were established. The load-carrying capacity, hysteretic behavior, fracture performance and energy dissipation capacity were compared, and the influence of the degree of widening on the seismic behavior of widened flange cover-plate connections with different degrees of weakening was discussed in depth. Finally, a design procedure was proposed to provide a basis for engineering application. The analysis results showed that widening the beam flange section can reduce the energy dissipation of the main frame and increase that of the cover-plate components. Widening the flange can also effectively transfer the position of the plastic hinge, and improve the effect and time of fuses. With the increase in the widening, the required design value of the bearing capacity was improved, which avoided excessive weakening and guaranteed the bearing capacity for normal use and the replaceable function of fuses. When the degree of widening reached a certain value, the influence of widening on the increase in the energy dissipation of cover-plate components was limited. Based on the calculation results, a relation curve of the limit value of bearing capacity coefficient and the widened flange coefficient was obtained. To ensure the full play of fuse, the design value of the bearing capacity coefficient should be less than the limit value, and the limit of the bearing capacity coefficient of the widened flange connection was 22% higher than that of the unwidened flange connection, indicating that the fuse effect will adequately exert with a smaller weakened degree of connection.