The work described in this thesis, 2-thioacetic acid benzothiazole chelate complexes. Infrared, ultraviolet–visible, spectrophotometric techniques, magnetic susceptibility, atomic absorption? conductivity measurement and other physical properties were used to characterize the free ligand and the above chelate complexes. All these compounds were act as stabilizer in PVC films. The rate of photodegradation and photostabilization of PVC film were monitored by measuring the carbonyl, polyene and hydroxyl indices (Ico, Ipo and IoH) values as afunction with irradiation time and ultraviolet–visible spectrophotometry using the concentrations of additive 0.5% wt/wt. The light of wavelength 313 nm. It is found that the carbonyl index polyene index and hydroxyl index values increased with irradiation time, and this increase depend on the type of additives. According to the experimental results obtained several mechanisms were suggested depending on the structure of the additives. Therefore HCl scavenging, UV absorption, peroxide decomposer and radical scavenger for photostabilizer additives were suggested.