A new device using dual quartz crystal resonators is proposed to determine the thermal property and morphological change of polystyrene. The resonators are installed in a small aluminum cell directly heated and air cooled according to the programmed temperature variation. The resonant frequencies of the dual resonators-one for reference and the other for sample-are measured and analyzed for the morphological change while their temperature varies. The temperatures of the changes are compared with the DSC thermogram and previously reported studies, and it is found that the measurements are comparable to those of the DSC. The proposed device is simple and easy to construct, and a portable system is available with some modification.