Stabilization standards of PVC films are fundamentally depend on essential laws: solvation and "reverberation" Stabilization. The photo-stabilization of poly(vinyl chloride) (PVC) films by epoxidized oleic acid was investigated. Photo-stabilization activities were determined by monitoring the carbonyl, polyene and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PVC with irradiation time were also tracked using tetrahydrofuran as a solvent. The quantum yield of the chain scission (Φcs) was evaluated and found with range 4.53´10-8 and 8.12´10-8. Postulated mechanisms were outlined depending on the structure of the additive.