In order to ensure the truss manipulator to meet the requirements of high precision, stability, reliability and large load carrying capacity in the process of high speed and large stroke, the kinetic characteristics are analyzed by the method of rigid-flexible coupling dynamics. Based on the basic structure and working flow of the truss manipulator, a rigid multibody dynamic model was established with SolidWorks-RecurDyn platform, then the contact stiffness of the gear rack and meshing rigidity of ball linear guide rail pair was also estimated with Hertz theory to ensure the accuracy of the model. Moreover, the flexible bodies of beam (RFlex) and sliding platform (FFlex) were built with RecurDyn-ANSYS, the rigid-flexible coupling dynamics model of truss manipulator eventually was established. Through the analysis of the rigid-flexible coupling kinetic characteristics, the influence of the flexibility of key components on the motion precision of the truss manipulator’s end-effector was studied, and the difference between the actual trajectory and the ideal trajectory of the equivalent mass center in the X, Y and Z direction were measured as ±0.06, ±0.72, and ±0.06 mm, which can reveal that the motion precision is ±0.72 mm, which can not meet the technical requirement of ±0.02 mm. Therefore, the reinforcement method is adopted to improve the cross section of beam. After the structural improvement, the motion precision is ±0.17 mm which meets the technical requirement.