Abstract: The thermal oxidation of polyacetylene (PA) was studied by thermogravity(TG) and infrared spectroscopy. Effects of polymerization catalysts and cis-trans configurations of PA and atmosphere were examined. Obvious induction effect was observed for the PA prepared with Nd-catalyst. Kinetic analysis of the TG data showed that the thermal oxidation was approximately of first order for both PA and O₂ concentrations and the apparent activation energy was 42?6kJ/mol for cis-PA and 51?6kJ/mol for trans-PA. Based on the variation of the IR bands with oxidation time, possible oxidation reactions were deduced.