A novel photo-induced homogeneous atom transfer radical polymerization (ATRP) system is constructed using an organic copper salt (Cu(SC(S)N(C2H5)(2))(2)) as a photo-induced catalyst at 30 degrees C. Herein, N,N,N',N '', N'''-pentamethyldiethylenetriamine (PMDETA) is used as a ligand, ethyl 2-bromophenylacetate (EBPA) as an ATRP initiator, and (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO) as a photo-induced radical initiator to establish an ICAR (initiators for continuous activator regeneration) ATRP using methyl methacrylate (MMA) as a modal monomer. The effect of the concentration of the organic copper on the polymerization is investigated in detail. It is found that well-controlled polymerization can be obtained even with the amount of (Cu(SC(S)N(C2H5)(2))(2) decreasing to a 1.56 ppm level, with the molecular weight of the resultant polymers increasing linearly with monomer conversion while maintaining a narrow molecular weight distribution ((M) over bar (w)/(M) over bar (n) < 1.3).