The complicated nonlinear characteristic of structures is largely responsible for bolted joints. In traditional structural dynamical analysis, the nonlinearity of the joint interfaces is ignored, or the linear method is used to model for bolted joints, which causes inaccurate analysis and increases the difficulty of studying nonlinear dynamic characteristics for bolted joints. The energy dissipation mechanism in bolted joints occurs as a result of micro-slip motion between rough surfaces in contact, which is studied by experiment. The hysteresis nonlinear characteristic of bolted joints is described by the Iwan model. The unknown parameters of the Iwan model are deduced by unconstrained nonlinear optimization and the Newton iteration method under quasi-static harmonic load, and the hysteresis nonlinear characteristic of bolted joints with the change in harmonic loading can be obtained. Finally, the experimental and numerical simulation results are compared to validate the Iwan model. The results show that the Iwan model can reflect the energy dissipation mechanism and the hysteresis nonlinear characteristic of bolted joints.