In response to the challenge of efficient prediction of the dynamic behavior of the dovetail-connected bladed disk systems involving boundary nonlinearity, rotating effects, complex loads, etc., the fixed interface modal synthesis method is applied to the reduced-order modeling of a rotating dovetail-connected bladed disk system. By introducing thin-layer solid elements on both groove and tenon contact surfaces to capture interference behavior, and considering the rotation-induced stiffening and softening effects as well as the dovetail joint-induced local load action, the reduced system-level model including the disk substructure, dovetail joint zone, and blade substructure under aerodynamic excitation is then established. The influence of the modal truncation numbers of the blade and disk on the first three natural frequencies of the reduced system is discussed, and the effects of rotating speed and friction coefficient on the modal characteristics and vibration responses of both the full and reduced models are compared with each other. The results show that: (1) within the studied parameter range, the maximum deviation of the reduced model in predicting the first three natural frequencies compared to the full model does not exceed 0.6%, and the maximum deviation in predicting the critical speed does not exceed 0.1%; (2) the nonlinearity of the dovetail connection makes the response spectrum of the system to exhibit multiples of the excitation frequency, and a smaller friction coefficient induces slip between the tenon and the groove thus leading to a quasi-linear component in the vibration response.