In the current practice of analysis and design of steel-framed building structures, the actual behaviour of beam-to-column connections is generally simplified to the two idealized extremes of either fully rigid behaviour or ideally pinned behaviour. However, most connections used in current practice actually exhibit semi-rigid deformation behaviour that can contribute substantially to overall displacements of the structure and to the distribution of member force. Some semi-rigid connection classifications have been presented and a nonlinear behaviour of semi-rigid connections is explicitly taken into account. On the basis of incorporate many research results made by other researchers, this paper has concluded the behaviours of all kinds of semi-rigid connection joints in terms of connection stiffness and strength, and some proposed calculating approach on these semi-rigid connection joints have been developed, which could be used in practice.