[23; 24] proposed a method for denoising and harmonic detection by using a non-orthogonal wavelet packet, which can isolate interference or non-coherent parts well. In terms of rotor dynamics of turboshaft engines, [PERSON] et al. [25] and [PERSON] et al. [26] established a finite element three-dimensional solid model of a turboshaft engine rotor by using ANSYS. Based on the ANSYS model, they studied the coupling vibration characteristics of a dual rotor with flexible supports. Based on the modal similarity criterion, [PERSON] et al. [27] designed a simulated rotor test bench for the turboshaft engine gas generator rotor. [PERSON] et al. [28] used SAMCEF to construct a dynamic model of a power turbine rotor and modified the supporting stiffness in consideration of the influence of stator. In summary, the above-mentioned research mainly focused on the natural characteristics of turboshaft engines with ANSYS. [PERSON] et al. [29] studied the unbalanced response of a double-disk rotor system with nonlinear support. [PERSON] et al. [30] used NASTRAN software to solve the modal parameters of the dual-rotor system and MATLAB to numerically solve the nonlinear dynamic response of the dual-rotor supported by SFD. [PERSON] et al. [31] took the double-rotor test bench as an example and, based on the finite element method, constructed the motion equation of the rotor system by using the fixed interface modal synthesis method and carried out experimental verification. [PERSON] et al. [32]used the transfer matrix method to calculate the critical speed, vibration mode, and unbalance response of a heavy gas turbine rotor. It can be noted that most researchers or scholars focused their attention mainly on impact effects originated from the blade off incident but seldom paid attention to the transient response characteristics of actual rotating machinery suffering from the blade off event. In most research cases, simple rotors (Jeffcott rotors or single-disk cantilever rotors) simulated with lower degrees of freedom (DOFs) or oversimplified rotor models are adopted to explore the dynamic characteristics under extreme working conditions such as blade loss. The gas generator rotor, which is the core component of the aero-turboshaft-engine, usually runs between the second-order critical speed and the third-order critical speed and has richer dynamic characteristics than simple rotors. At present, works on the dynamic response of the turboshaft aero-engine with blade off are not reported. In addition, previous research on the dynamic modeling of aero-engine rotors mainly takes aeronautical twin-rotor engines with intermediary bearing coupling as the research object and basically simplifies the inherently complex rotor structure to a straight shaft plus rigid disk associated structure, which neglects the main structural features of the rotor and is unable to obtain dynamic characteristics consistent with reality. For the gas generator rotor used in the turboshaft engine, there is very little research on its dynamic modeling and response analysis. This is no doubt because the previous dynamic models based on constant-section beam elements or ANSYS solid elements are difficult for characterizing variable-section rotors with complex profiles, the calculation cost is very large, and the conclusions or laws obtained provide limited guidance to the actual engineering. Obviously, the vibration laws obtained by the simplified rotor in the past are no longer simply applicable to those complex turboshaft engines. Therefore, it is extremely necessary to establish a dynamic model, with a small calculation time and characterizing the complex structure of the rotor well, in order to obtain response characteristics that can guide the actual situation. Therefore, this article focuses on complex rotor dynamics modeling and transient response analysis, with the purpose of providing more valuable guidance for engine rotor dynamics design.