To investigate the effect of varying temperature on the modes of structures, a set of experimental systems is designed to provide a temperature-controlled environment. An experiment is conducted on a TC-4 titanium alloy cantilever beam in a temperature-varying environment, and a modal parameter identification method based on time-frequency analysis (TFA) is applied to process the response signals of the beam to estimate time-varying modal parameters, including natural frequencies and mode shapes. The results show the future application of the TFA-based modal parameter identification method for the estimation of time-varying modal parameters. The results reveal the thermal effect on the modal parameters, thus providing a valuable signal-processing method for investigating the dynamical properties of structures in a temperature-varying environment.