The mechanism and efficiency of chlorine removal by calcium in different atmospheres were investigated by means of thermogravimetry.The PVC was used as the chlorine emission source.The results indicated that PVC can be used as the chlorine emission surce.The efficiency of chlorine removal by Ca(OH)\-2 is the best in the three calcium compounds.The mechanism of chlorine removal by Ca(OH)\-2 is the same as by CaO.The chlorine removal mechanism in different atmospheres is individual.CaCl\-2 will be decomposed under high temperature.