Abstract: Under the impacted of solar heat flux, the satellite antenna in orbit is prone to thermally induced vibration or inaccurate pointing, which will lead to spacecraft failure in serious cases. In this study, a modeling and model order reduction method for rigid flexible thermal coupling multibody system based on the improved component mode synthesis method is proposed. First of all, the displacement and temperature field of the flexible antenna are discretized by the unified element shape function of the absolute node coordinate formulation (ANCF), which can avoid the mapping error and efficiency problems caused by the mismatching of the two physical fields. The ANCF reference node is used to describe the central rigid bodies. In addition, the solar heat flux input and the surface emitting radiation are considered in the system equation. According to the highly nonlinear characteristics of the tangent stiffness matrix of the ANCF, the first-order Taylor expansion is used to linearize the dynamic and heat transfer equations. The tangent stiffness matrix in the linearized horizon is a constant matrix, which avoids the iteration of the elastic force and its Jacobian matrix in each time step, and makes the model order reduction method could be applied. Afterwards, the improved component mode synthesis method is used to divide the substructure and reduce the degrees of freedom of the system. The substructures are connected by constraint equations to ensure the accuracy and continuity between the structures. At last, four numerical examples such as the pure heat conducting semicircular thin plate, the thermal expansion of thin plate, the flexible solar panel and the rigid flexible thermal coupling parabolic antenna are given to verify the effectiveness of the proposed method. The results show that the proposed method can reduce the scale of the system and improve the efficiency of simulation calculation without losing accuracy.