Z-shaped folding wing presents multiple forms during a flight and the structural dynamical feature varies with its forms. So the research on the modal characteristics is important to investigate its structure. First, the modal analysis technology and the fundamentals of PolyMAX algorithm are reviewed. Then, modal experiments are conducted on the Z-shaped folding wing at different forms based on the experimental modal analysis (EMA) and operational modal analysis (OMA). Finally, the parameters of the first five orders are validated. The results show that folded angles have significant impact on the structure stability. Particularly, the structure is stablest when the folded angle is 90°.