Abstract: In order to study the effects of fastener clamping force failure on dynamic performance of vehicle-track system, a detailed fastener model was established in the paper, and the vertical nonlinear stiffness behavior of the WJ-8 fastener in different stages was analyzed. An improved bilinear tension stiffness spring model and a no-tensioned spring model were proposed to represent the invalid fastener. The influence of different failure types of fasteners on dynamic response of vehicle-track system was also analyzed. The results show that, the vertical stiffness of the fastener can be divided into two parts: uplift stiffness and compressive stiffness. When the uplift force exceeded the clamping force, the vertical uplift stiffness of the fastener would decrease rapidly and the fastener would lose its constraints on the rail uplift deformation. Both clamping force failure and complete failure of fastener would weaken rail constraints and increase vibration. Clamping force failure mainly increases the vibration of rail in 8 Hz-50 Hz central frequency band, while the complete failure brings an increase in the whole frequency band.