The oblique impact dynamic analysis for a flexible manipulator system with large overall motion is studied in this paper. Based on the rigid-flexible coupling dynamic theory of flexible multibody system, the coupling deformation item is considered to reflect the coupling effect of the large overall rigid body motion and the small elastic deformation motion. The rigid-flexible coupling continuous dynamic equations of the system are then derived through the use of the Lagrange dynamic method. The oblique impact dynamic model for the system is developed by introducing a oblique impact model which includes the normal impact model and the tangential impact model. Meanwhile, the impact forces are added to the system dynamic equations in form of the generalized forces. A nonlinear spring damper model based on the continuous contact force method is set as the normal impact model, while a modified Coulomb friction model, which describes the friction force of the whole process with a unified equation, is set as the tangential impact model. The contact separation criterion is also established to identify the dynamic status and realize the transformation between the continuous dynamic model and the oblique impact dynamic model. Moreover, the impact dynamic simulation examples are given to verify the oblique impact dynamic modeling method, and the dynamic behaviors in the global simulation process are discussed. The results show that the impact makes a great effect on the large overall motion and the small deformation motion both in the impact process and the un-impact process. The dynamic parameters, such as the displacement, the deformation, the mechanical energy and the impact force are also compared at different impact angels.