Multiple flight modes and high maneuverability are typical characteristics of coaxial high-speed helicopters, making conventional separated flight/engine control strategies inadequate for high-performance control requirements. At the same time, the high dynamic coupling across the entire flight envelope, strong external disturbances, and time-varying flight characteristics pose severe challenges to the robustness of control strategies. Therefore, this paper proposes an integrated flight/propulsion control architecture based on robust explicit model following control(REMFC). First, a comprehensive flight/propulsion simulation model is developed, incorporating the coaxial helicopter, turboshaft engine, and transmission system, based on the torque–speed relationships of the rotor and engine. Next, by reconstructing the feedforward–feedback structure of explicit model following control and introducing an extended state observer(ESO), a robust explicit model following control strategy is proposed. This strategy enables online estimation and compensation of unmodeled dynamics, aerodynamic disturbances, and parameter uncertainties, and the closed-loop tracking error is proven to be uniformly bounded. Finally, based on the robust explicit model following control strategy, an integrated flight/propulsion control law is designed, achieving coordinated control of flight commands and engine speed. Multi-mission simulation results across the full flight envelope demonstrate that the REMFC-based integrated control approach for coaxial high-speed helicopters outperforms conventional methods in reference tracking, disturbance rejection, and rotor speed stabilization, significantly enhancing flight performance and robustness under complex flight conditions.