Under both pyrolysis and combustion condition, HCl removal efficiency for medical waste with Ca-based additives was semi-quantitatively studied by means of TG-FTIR. Additionally, the difference of HCl removal efficiency for PVC and medical waste was compared. Experimental results showed that: 1) Thermal degradation of medical waste mainly took place in two steps under both pyrolysis and combustion condition; 2) HCl emitted at both two steps and HCl concentration increased with the increased of Cl ratio in the medical waste; 3) for the same additive, HCl concentration decreased with the increased of additives amount, that is to say, HCl removal efficiency of medical waste increased as the increased of Ca/Cl molar ratio. Fourth, when Ca(OH) was used as additive, HCl removal efficiency for medical waste combustion was a little higher than that for medical waste pyrolysis, but either CaCO or CaO was used as additive, it was just opposite, more specifically, when CaCO was used as additive with Ca/Cl=1.3, HCl removal efficiency was 5.49% under pyrolysis condition, but that was only 4.24% under combustion condition. Fifth, under the same Ca/Cl molar ratio, HCl removal efficiency for PVC was higher than that for medical waste under both pyrolysis and combustion condition, more specifically, when Ca(OH) was used as additive with Ca/Cl=1, HCl removal efficiency was 64.51% for PVC, but that was only 27.66% for medical waste pyrolysis with 4% Cl under pyrolysis condition.