Abstract: By employing the component method, an analytical model to predict the initial rotational stiffness of angle steel tower K-joints is set up. It is considered that the connection rotation is mainly induced by the deformation of the main angle in shear, bolts in shear, and the hole-wall in bear. Considering limb in shear as short column with shear deformation mainly, superposition principle is used to calculate initial stiffness of a joint. Consider bolts as Timoshenko beam, using the principle of virtual work and unit-load method to calculate its shear rigidity. Combining the five full-scale tests, the mechanical model is qualified. Test results reveal that the mechanical model is reasonable. Parameter analysis show that the number and spacing of bolts are the most important factors to decide joint’s initial rotational stiffness, and that others such as limb wide and thickness, bolt diameter, and joint plate thickness also have a certain effect on initial rotational stiffness.