The work aims to molecular structure of Parafilm by infrared spectroscopy. The one-dimensional variable temperature infrared spectroscopy, second derivative variable temperature infrared spectroscopy, fourth derivative variable temperature infrared spectroscopy and deconvolution variable temperature infrared spectroscopy of Parafilm were respectively studied by Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR). There were mainly eight infrared absorption modes, including CH3 asymmetrical stretch vibration, CH2 asymmetrical stretch vibration, CH2 symmetrical stretch vibration, CH2 scissoring vibration, CH3 asymmetrical scissoring vibration, CH3 symmetrical scissoring vibration, C—C skeleton stretch vibration and CH2 in plane rocking vibration in Parafilm. The finalized main molecular structure of Parafilm was polyisobutene. In the temperature range of 293~393 K, the Parafilm thermal stability was further studied by variable temperature ATR-FTIR. The thermal stability of Parafilm was poor and its critical operating temperature was 313 K. The study has expanded the key roles of variable temperature ATR-FTIR in the analysis of structure and thermal stability of the polymer packaging materials.