A waste incineration atmosphere was simulated as HCl/H2O/O-2/CO2=N-2, in order to experimentally study chlorine behavior as temperature ranges from 1173 to 1473 K and residence time varies. The results show that Cl radical, produced by the decomposition of HCl at high temperature mainly recombine to form Cl-2 and HCl at the quenching section. It was found that temperature, residence time, cooling rate and feeding gas composition influence Cl-2 concentration. In addition, thermodynamic equilibrium calculations performed to understand the behavior of chlorine for this reaction system. In spite of the discrepancy existing between experimental and calculation results, similar trends have the capability to describe the behavior of chlorine.