Abstract: Experimental results abroad indicated that the cover-plate rehabilitated steel moment connection exhibits good loading capacity, with the failure mode of the plastic hinge formed on the beam beyond the reinforced region. However, few studies have been carried out on the rehabilitation of the connection with initial loading. Based on the stress distribution obtained by the finite element analysis, some assumptions are made and a mechanical model is proposed. The mechanical behaviors of the rehabilitated connection with initial loading have been investigated. By the simplified model, the distribution pattern of the initial loads and the additional loads between the cover plates and the original connection is obtained. The design of the rehabilitated connection with initial loading as integrated joint is no longer applicable; neither is the traditional beam theory. The length of the cover plate imposes less influence on the moment distribution between the cover plates and the original connection, but the thickness of the cover plate is the main design parameter.