Abstract: Plasma pyrolysis of polypropylene has been tested for the propose of converting waste plastic into gaseous fuel and useful chemicals.The plasma reactor has a D.C. arc nitrogen plasma generator with maximum input electric power of 55 kW and a reaction chamber of 50 mm inner diameter and 1 000 mm height. The results of a series of experiments show that under our optimum experimental conditions of power input 35.2 kW, feed rate 60 g/min, the concentration of H2 and C2H2 at the exit of the chamber can be as high as 18% and 5% respectively. The steam injection is introduced for improving the gaseous product quality. With water steam injection, the sum of H2, CO in the gas products can reach to 40% while the decrease of C2H2 concentration is slight. Meanwhile 96% of solid conversion and gas productivity of 2 160 mL/g are achieved. The results indicate that plasma assisted thermal decomposition of polypropylene may be a useful way for recovering energy and useful chemicals from waste plastic.