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The unique structure of hybrid robot makes its dynamic characteristic different from that of the traditional machine tools. Therefore, the dynamic model is crucial to both designing and application of hybrid robot. In this paper, a new type of 5-DoF hybrid robot is introduced and its dynamic model is established. Firstly, the kinematic formulas are derived for all the component, and then the inertia forces or moments are calculated. Secondly, the active forces or moments in the joints are assumed as variables and the number of variables is reduced by analyzing joint types. Then an equation set of 36 equilibrium equations with 38 variables is obtained by using D'Alembert's principle. Based on the spatial deformation compatibility analysis of 2 branches, 2 supplementary equations are derived to determine the solution of dynamic model of the hybrid robot with redundant constraints in its parallel mechanism. Several cases are studied by comparing with ADAMS simulation. The result shows the good accuracy of the proposed dynamic model, which provides a practical method to calculate the reaction force or moment in any joint at any instant for the hybrid robot and thus facilitates dimensional synthesis, trajectory optimization and smoothing control.