<p>The chemical precooling variable cycle engine (CP-VCE) can operate at high Mach numbers, but the precooler does not work efficiently at low Mach numbers and low altitudes, which negatively affects the engine performance. To achieve highly efficient operation of CP-VCE in the full speed domain range, this paper conducts the research of CP-VCE performance optimization method. First, the precooler simulation model, based on the ε-NTU method is established, and the thermodynamic framework of CP-VCE is also established. In addition, the effects of adjustable guide vanes and dual-fuel precooler on the engine performance are investigated. Finally, a performance optimization method based on the AWOA (Adaptive Adjustment Whale Optimization Algorithm based on Weights and Search Strategy) algorithm is proposed to optimize the guide vane angle and fuel ratio as optimization variables for the conventional operating point and climb path point. The results show that the optimized engine has a reduced fuel consumption rate in turbofan mode and increased average thrust in turbojet mode. In this paper, the performance optimization of the CP-VCE in different modes is realized, and the improvement direction of the engine performance is given according to the relevant results.</p>