Abstract: The ultra-large capacity end-plate connection is a new beam-to-column connection type that can be applied in steel structures with large spans or heavy loads. To consider the resistance and rotational stiffness of this connection type accurately in structural analysis, it is necessary to determine the moment-rotation curves of the connections. A component model of ultra-large capacity end-plate connections was proposed based on the existing experimental results and finite element analysis results, and a new component form was introduced with the methods to analyze its resistance and stiffness presented. Also, methods to calculate the moment resistance and the rotational stiffness of ultra-large capacity end-plate connections were proposed based on component method. Combining the advantages of the existing typical moment-rotation models, a moment-rotation model, taking the moment resistance and the rotational stiffness as basic parameters, was proposed for this connection form. The results of the proposed methods were compared with the results of the existing experiments and finite element analysis, demonstrating that the proposed method can predict the moment resistance and the rotational stiffness with a satisfactory accuracy while the moment-rotation curves obtained by the proposed model show good agreements with the experimental curves.