<p>To address the difficulty of modeling and predicting the spatial attitude-dependent frequency response function (FRF) of the robot, in this study, the frequency response characteristics of a 2UPU/SP + RR hybrid robot were investigated, and a complete set of methods for modeling and analyzing robot dynamics were provided. The kinematics of the hybrid robot was analyzed to obtain the spatial attitude relations among the components during motion. The complex hybrid robot was equated to an assembly of several substructures and joints, and the dynamics of the joints were modeled. Considering the flexibility of substructures and joints, an FRF prediction model of the hybrid robot end was established based on the generalized receptance coupling substructure analysis (GRCSA). Retaining important geometric features, the substructures were simplified, and the FRF matrices of substructures of the hybrid robot were calculated. The joint stiffness and damping in the non-driving directions were further considered, and the critical joint was modeled in more detail. The calculation method of the unknown joint parameters was described. Based on the improved prediction model, the FRFs of the hybrid robot end in different spatial attitudes were predicted. For the natural frequencies in the <i>x</i>, <i>y</i> and <i>z</i> directions, the maximum errors of the prediction model are 1.508%, 0.626% and 2.187%, respectively. The influence laws of joint variables on the frequency response characteristics of the hybrid robot were analyzed in a wide range of spatial attitudes. The methods in this study are general, and can provide ideas and references for the dynamic analysis of other complex machines.</p>