In this paper，a new method for nondestructive detection of the geometric features of thin films using a portable single-port surface acoustic wave（SAW）resonator based on lithium niobate（LiNbO₃）is presented. The measured thin-film structures include single metal，double-layer，and Damascus-structure films. After simulating the S-parameter curve using the finite element method，we obtained the relationship curve between the resonant frequency of the SAW resonator and the corresponding geometric parameters in a certain range through fitting，which was expressed using a third-order polynomial. The results showed that the coefficient of determination R² of the fitting curve representing the relationship between the geometric features and resonant frequency obtained by fitting the finite element simulation results can exceed 0.999 0，and the fitting polynomial can accurately characterize the relationship between the geometric features and resonant frequency of the resonator. The resonant frequency of a sample with unknown geometric dimensions was measured using the proposed method and substituted into the corresponding formula to calculate the geometric dimensions of the sample. The results showed that the SAW resonator has significant potential for the rapid non-destructive detection of thin-film geometric features.