Abstract: A new method to calculate rotational deformation of structural steel beam-to-column semirigid end-plate connections has been proposed in this paper.It has been verified by the relevant tests results that this method can calculate the integral rotational behavior of end-plate connections including the initial rotational stiffness and the moment-rotation(M-φ)curve accurately.Furthermore,it can analyze and calculate each source of joint rotational deformation including the shear deformation of the panel zone,the bolt extension,the bending deformation of the end-plate and column flange,etc.As a result,this method can provide the moment-shear rotation(M-φ_s)curve and moment-gap rotation(M-φ_ep)curve,which provides reliable calculational basis for analyzing the detailed rotational behavior of end-plate connections.This method presents a supplement to the steel structure design code of our country.