As future aircraft continue to develop towards “wide-speed, wide-altitude,” the power systems that provide propulsion are also receiving extensive attention and research. The hydrogen intercooled adaptive cycle engine (HI-ACE), as a new type of high-speed turbine configuration that integrates the advantages of variable cycle and precooling technologies, is considered an effective and feasible solution for supporting high-speed aircraft applications. For the design of engines, modeling and simulation in a digital environment are indispensable. However, the complex configuration and modes of the HI-ACE significantly increase the simulation complexity. Therefore, this paper focuses on the overall performance simulation technology for the HI-ACE: Firstly, the mathematical modeling of innovative components, represented by the intercooler heat exchanger (IHE), is completed, and an engine simulation model is established based on a modular approach. The developed model meets the requirements of overall performance simulation. In addition, the proposed multi-mode variable guess value and equation system dimensionality reduction method, along with the temporary storage component characteristic map interpolation logic, can achieve a 45%-50% improvement in computational efficiency. This simulation technology can effectively support the overall performance simulation, design, and optimization of complex engine configurations.