The gaseous products of co-pyrolysis of waste tires a nd biomass under DC arc plasma condition were investigated.The results showed that the volumetric concentration of acetylene in carbon-containing gases obtained when waste tires, biomass and coal were separately pyrolyzed was 14.6%,13.7% a nd 10.6% respectively when the parameters experimental run were 150 A of electr ic current, 310 V of voltage,2.0 m3·h -1 of flux of argon, 0.65 m3· h -1 of flux of main hydrogen, 0.4 m3·h -1 of flux of auxiliary hy drogen and 5.0×10 -4 kg·s -1 of feed rate.Under the same condition, the volumetric concentration of acetylene in carbon-containing gases produced from the mixtures of biomass and waste tires when the mass ratio of biomass and waste tire was 1/2 increased obviously,nearly 2—3 times that of tires or biomas s pyrolyzed separately.The concentration of acetylene was closely related to the volatile matter and the amount of oxygen.In addition, the possible mechanism of the pyrolysis occurred under plasma condition was proposed.