A high-quality polyene can be obtained by exensive dehydrochlorination of poly(vinyl chloride) (PVC) in aliquid/solid two-phase system. The liquid phase is a tetrahydrofuran solution of PVC containing a small amount ofpoly(ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles.The structure of the polyene is polyacetylene-like and has a long conjugated C=C sequence and a narrow dispersity ofpolyene sequences according to its FT-infrared and Raman spectra. The environmental stability of the polyene was alsostudied by IR, Raman spectra and elemental analysis. Experimental results demonstrated that the polyene was susceptible toair and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups. The polyenesequences were shortened and its dispersity became broader due to the effect of dioxygen. A high-quality polyene can be obtained by exensive dehydrochlorination of poly (vinyl chloride) (PVC) in aliquid / solid two-phase system. The liquid phase is a tetrahydrofuran solution containing a small amount of poly (ethylene glycol) with molar mass of 400 g as a phase transfer catalys. The solid phase is potassium hydroxide particles. The structure of the polyene is polyacetylene-like and has a long conjugated C = C sequence and a narrow dispersity of polyene sequences according to its FT-infrared and Raman spectra . The environmental stability of the polyene was alsostudied by IR, Raman spectra and elemental analysis. Experimental results of the polyene was susceptible toair and could be changed into a material containing high concentrations of hydroxyl and carbonyl groups. The polyenesequences were shortened and its dispersity became broader due to the effect of dioxygen.