In the process of spheroidization audio detection, the selection of exciting position directly affects the amplitude of the modal frequency response of each order directly. For similar modal frequency responses, it is likely to affect the measurement results. In order to extract the modal frequencies of interest and suppress the modal frequencies of no-concern, a finite element-based optimization method for exciting position is proposed. Taking the car’s part flywheel as an example, modal analysis is performed on the spheroidal graphite cast iron test piece through ANSYS, combining the characteristics of each order mode, natural frequencies and modal excitation theory to determine the optimal excitation point, and the audio signal of the exciting positions is analyzed by MATLAB GUI verification. The experimental results show that this method can effectively stimulate the modal shapes required for the observation of the flywheel structure. It is verified that the close modal frequency response is closely related to the choice of the exciting position. Effectively distinguishing modal shapes of similar frequencies has strong practicability.