Abstract: In order to determine the effect of composition and chlorine content in medical waste on PCDD/Fs（polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans）distribution，pyrolysis-combustion experiments were conducted with single component，two components and different chlorine contents. Results indicated that plastics with different chlorine content are different in both of PCDD/Fs generation and the concentration of chlorinated congeners. When PVC was combusted together with fiber，PCDD/Fs formation was enhanced，and the higher chlorinated congener was noticeably increased，which was varied with different PVC type. With the increase in chlorine content，the amounts of HxCDF，HpCDF and OCDF increased. No significant correlation between the total chlorine level in the fuel and the emission level of PCDD/Fs was observed. While，the yield of PCDD/Fs showed a conspicuous increase when chlorine content exceeded 1.73%. Furthermore，the PCDD/Fs formation characteristics were different for different PVC type even with the same chlorine content.