UV polymerization mechanism of acrylic adhesive for optically clear resin (OCR) was examined. The polymerization mechanism was mainly controlled by the acrylic monomer composition and the photo-initiator concentration in the syrup of acrylic adhesive as well as UV exposure time and intensity. It was found that adhesion properties (peel strength) of acrylic adhesive affected by the degree of polymer conversion in syrup. The degree of conversion could be expressed change in enthalpy (photo-DSC), chemical structure (IR) and residual monomers (TGA). It also influenced the rheological behaviors which were important processing parameters for OCR coating. Keywords: UV polymerization, UV-curing coating, optically clear resin, degree of conversion