The core of the model-based systems engineering （MBSE） method is to establish high-quality integrated models.Model assembly is the foundation for realizing MBSE integrated modeling，since single-point models are difficult to ensure the support and maintenance of the functionality and performance of an entire system.In this paper，based on the single-point MBSE models of launch vehicle systems constructed in recent years，the top-down model assembly methods are investigated.A high-level and extensible top-level model tree is built，and the assembly sequences and methods for various professional MBSE models are clarified.Finally，taking the overall performance，trajectory，and aerodynamics as examples，the construction of an integrated MBSE model for launch vehicles is realized，accelerating the transformation and implementation of MBSE.