Mechanism of polymer scale deposition on internal wall of kettle and surface of its parts in polyvinyl chloride(PVC) production was studied. A series of polyhydric phenols were synthesized as preventive agent of polymer scale deposition. Production of blue polymer scale preventive agent was industrialized. The recipe was optimized in term of good product properties and quality stability. Performance of the product was demonstrated in a PVC plant and satisfactory effect of preventing polymer scale deposition was achieved.