This paper proposes an efficient semi-analytical elastodynamic modeling approach for predicting the low-order dynamic of a hybrid machining cell. The system is composed of two subsystems: a hybrid robot and a machine frame. First, the elastic dynamic models of motion of limbs within the hybrid robot are developed using the Matrix Structure Analysis, and super-element models are constructed via the Component Mode Synthesis (CMS) approach. Subsequently, the dynamic model of entire system is established by assembling the super-element models of the hybrid robot and the machine frame. To further improve computational efficiency, mode synthesis approach is applied again to reduce the degrees of freedom of the assembled system. Experimental modal testing is conducted on a physical prototype to validate the proposed model. The results show that the predicted natural frequencies and frequency response functions at the spindle end face center point exhibit strong agreement with experimental measurements, thereby confirming the accuracy and effectiveness of the proposed modeling approach.