Polymerization of a series of unsaturated acrylate monomers were initiated with photoinitiator under the irradiation of UV LED light. The change of iodine value in reaction system could represent reaction rate. The effects of photoinitiator content on the reaction rate, molecular weight and molecular weight distribution were investigated. The structure of polymer was also characterized by FT-IR. The unsaturated acrylate monomers reaction rates is acrylate monomers > vinyl acetate > methyl acrylate monomers > styrene. For active acrylate monomers, such as butyl acrylate (BA), methyl acrylate (MA), acrylic acid-2-ethyl hexyl ester (2-EHA), the appropriate mass fraction of photoinitiator is 0.5%～1%. For inactive methyl acrylate monomers, such as butyl methacrylate(MBA), methyl methacrylate (MMA), the appropriate mass fraction of photoinitiator is 1%～1.5%. The molecular weight decreases with photoinitiator content. The molecular weight distribution decreases first and then increases with photoinitiator content.