Abstract: Effects of chlorine on heavy metals migration at different temperatures were studied in a quartz tube under nitrogen atmosphere by adding inorganic chloride (NaCl) and organic chloride (PVC) during pyrolysis of hyperaccumulator biomass. The results indicated that NaCl or PVC additives could make an increase of heavy metals evaporation. For Cd and Pb, the PVC had much more impact on heavy metals migration characteristics than NaCl. For Zn, Mn and Cu, the order was contrary. The results also indicated that, excepting Cd, in the same chlorine content conditions, the heavy metals evaporation had no large change with the temperature increased from 400 to 700 °С. Only at higher temperature (above 700°С), the distinction could be detected. At the temperature of 900°С, Cd, Pb and Zn were volatile completely whether chlorine were added or not. In the experimental range, the maximum evaporation rate of Mn and Cu were 66.15% and 66.99% respectively, leading to higer Mn and Cu contents in bottom ash.