The granules of waste tire were pyrolysed under vacuum condition in the temperature range of 450 ℃～600 ℃, and the effects of the temperature and basic additives of Na2CO3 and NaOH were studied. The results show that the pyrolytic oil yields reach the maximum of about 48% at 550 ℃ under vacuum condition without additive. 3% NaOH could facilitate the pyrolysis reaction markedly with the maximum oil yield of 49.66% at 480 ℃ and then decrease with increasing temperature. However, the effect is little on pyrolysis of tires when 3% Na2CO3 is added. Tire pyrolysis gas, determined by gas chromatography with TCD and FID detectors, is mainly H2, CO, CH4, CO2, C2H4 and C2H6, etc. Relative content of H2 in the pyrolysis gas increases obviously in the presence of NaOH, more than 60%, but those of CH4, CO and C2 decrease. The composition of gaseous product also varies with temperature. Pyrolytic oil fractions was distilled to recover the pyrolytic naphtha (i.b.p～205 ℃). Qualitative and quantitative analysis of the pyrolytic naphtha were carried out by GC and GC-MS. It is illustrated that dl-limonene is the main component, with more than 11% concentration of the pyrolytic oil which is a chemical product with high economic value and wide industrial applications.