A dynamic model of flexible translational joint with Karnopp friction is presented in this paper. The slider of translational joint is treated as flexible body, while the guides are treated as rigid. Meanwhile, the influences of clearance on the dynamics of systems are considered. Since the friction forces and contact states between the slider and guides are complicated, a mechanical model is proposed using finite element method, where a contact model is developed based on Penalty method and the timevarying contact states of nodes are determined by applying trialanderror algorithm. Based on KED method and Newmark method, a simulation method is proposed to solve kinetic equations of the translational joint. Eventually, a planar sliderbar system with Karnopp friction and flexible slider is simulated, and the dynamic response of the mechanical system is analyzed. Moreover, the numerical results reveal the reasonability of the new developed method.