This paper presents the mode synthesis method for structures with nonlinear connective parts. The mode synthesis method is applied to large structures in order to decrease the computational loads of the dynamic analysis. The structures are divided into substructures in the mode synthesis method. The connective parts between substructures have been treated as linear spring models with viscous damping. However, the nonlinearity cannot be neglected in many cases. The connective parts between substructures are modelled by nonlinear systems considering the friction and the gap. The mode synthesis method is applied to a truck crane model with nonlinearity. The dynamic responses are numerically evaluated using the Newmark-β method. A crane boom model with a wire rope is treated as a model example. The dynamic responses of the crane boom operated in swing motion are calculated.