In this research the radical chlorination reaction of polyethylene has been carried out in an aqueous slurry process via chlorination of high-density polyethylene under amoderate pressure, using chlorine gas and UV irradiation. These processes were performed in two-stage subsequently. First step was at low temperature below the crystalline melting point, and the second was above that temperature. Three types of chlorinated polyethylene were produced that were included 6.5, 12 and 34 percent by weight of high-density polyethylene. These three types of chlorinated polyethylene were characterized by Fourier transform infrared (FTIR) spectra and were compared with polyethylene and polyvinyl chloride. The comparisons of these spectrums show the progress of reaction. The content of chlorine was confirmed by an elemental analyzing technique namely flask combustionmethod (DIN EN ISO1158) and the results interpreted accordingly. The results of screening analysis on product were reported too.