Abstract: Based on the current available research, the stiffnesses are developed for the column web in compression, tension and shear, rebar in tension, column flange and end plate in bending flexure, concrete slab in compression, etc. Based on these stiffnesses, a method has been developed for predicting the initial rotational stiffness of semi-rigid composite beam-to-column joints with a flush end-plate connection by the component method. In this method, the effects of both negative moment and positive moment are taken into account. Comparisons against experimental results have demonstrated that the method is capable of predicting the initial stiffness of flush endplate connections with very good accuracy, and can be used to calculate the initial rotational stiffness of the full shear connection and the partial shear connection composite joints.