The purpose of the present study was first, to evaluate the relationship between composite surface conversion and surface discoloration, second, to know if there was difference in surface discoloration between celluloid-strip-finished composite surface and polished surface. In addition, the discoloration of composite surface was also evaluated with visual inspection or digital camera with high resolution monitor, Z100, Tetric Ceram, Spectrum, and Aelitfil were used. The composite surfaces were celluloid-strip finished (group 1), polished (group 2), celluloid-strip finished under nitrogen gas purging (group 3) or only light cured without finishing or polishing under nitrogen gas purging (group 4). The microhardness of each samples were also measured in each group. The samples of each group were also divided into 4 subgroup whether they were immediately placed in disclosing solution (0.2% Elythrosin, pH 7.0) (subgroup1), 1 day after light curing(subgroup 2), 3day after light curing(subgroup 3) or 7 day after light curing(subgroup 4). The computer controlled spectrophotometer was used to determine CIELAB coordinates ($L^*$, $a^*$, $b^*$). The amounts of color difference were compared. The results were as follows; 1. There was no difference in discoloration between celluloid strip finished composite surface and polished surface. 2. The samples discolored more when they were placed in disclosing solution immediately after polymerization than other groups. 3. When the samples were light cured under nitrogen gas purging and without polishing process, they discolored more than other groups even though they showed higher micro hardness. 4. With visual inspection or digital camera, only a limited information was available in detecting composite surface discoloration.