Abstract: Modal decomposition methods are effective techniques for rapidly identifying key features and extracting essential information from flow fields. However, rotor flow fields are highly unsteady and nonlinear, often more complex than those of fixed-wing aircraft. Traditional proper orthogonal decomposition (POD) yields modes with multiple frequency components, making it challenging to accurately capture dynamic characteristics. To deeply analyze the flow features and evolution of rotor flow fields, the dynamic mode decomposition (DMD) method is introduced. Utilizing the National Numerical Wind Tunnel (NNWT) HeliX software, simulations of the Robin fuselage interference model were conducted, and DMD-based decomposition and reconstruction of the rotor flow field were performed. Key flow modes, their frequencies, and growth characteristics were obtained. A reduced-order model was established, and reconstruction errors under hover and forward flight conditions were analyzed. Results demonstrate that the DMD method effectively extracts dominant flow features and retains critical information for reconstruction, providing methodological support for studying vortex evolution and interference mechanisms.