The degree of conversion of visible light-cured resins was examined. The optimum composite photoinitiator composition, and the degree of conversion after polymerization, of visible light-cured resins, were determined. As a monomer, triethyleneglycoldimethacrylate (3G) was prepared for the visible light-cured resins by changing the kind of photoinitiator. As photosensitizers, camphorquinone (CQ) , benzanthron (BA) , dibenzoyl (DB) , thioxanten-9-one (T9) , 8-quinolinesulfonyl chloride (QC) and 3-phenyl-5-isoxazolone (PIO) were used.As a reducing agent, methacryloxyethyl-p-dimethylaminobenzoate (DMAB-EMA) was used. As an inhibitor, 2, 6-di-tert-butyl-p-cresol (BHT) was used, The basic photoinitiator composition (here in after NON) was CQ 0.30wt%, DMAB-EMA 1.40wt% and BHT 0.01wt%. The composite photointiators were made of NON and one-three photosensitizers. Trial resins were examined by FT-IR using the liquid film method. The infrared absorbance measurement were made before irradiation and chronologically repeated after the resins had been polymerized by irradiation for 90sec. The quantity of the remaining double bond (RDB) of all trial resins, except BA-PIO system resins, decreased linearly with the logarithmic time after the start of irradiation. The BA-PIO system resins showed an induction period. When the photosensitizer was added to NON, the order of the conversion at 5min after the start of irradiation was:QC>DB>T9>NON>BA. The most appropriate photosensitizer to be mixed with NON was QC, and the optimum mixing ratio was 0.30wt% to monomer.