Aerospace thin-walled parts are characterized by large material removal rate and poor workpiece rigidity. It is very easy to occur chattering phenomenon during milling processing, which affects the machining efficiency and quality of the workpiece. Before cutting thinwalled parts, dynamic modeling and analysis are needed to extract the modal parameters of the contact area between tool and workpiece to predict the forced vibration and avoid the chatter. In this paper, the finite strip method for dynamic modeling and analysis is derived, and then used to predict the frequency response function at the weak point of the parts. The corresponding T-type and B-type test parts are designed, and the accuracy of the model calculation results is verified by modal hammer test. By comparing the modeling calculation results with the experimental test results, it is found that the frequency calculation errors of the dominant mode of frequency response function at the weak point of the thin-wall parts are all less than 3% and the amplitude calculation errors are all less than 7%. Therefore, the finite strip dynamic modeling method proposed can be used to predict the frequency response function of thin-walled parts.