After clinical adjustment of dental casting restoration, re-polishing procedure is recommanded because the smooth gold sureface is lost. But there is the possibility to get more loose contact than that intended by loss of gold alloy according to the kinds of polishing materials and polishing time. Therefore in this study I polished type II gold alloy with 390gm force, 20,000rpm speed, and 8 kinds of gold alloy polishing materials, fabricated by 4 companies and then measured the amount of loss of gold alloy with Surfcorder SEF-30D and observed alloy surfaces polished by 3 brown rubber points with SEM. The amount of loss of gold alloys polished with 8 kinds of polishing materials and the degree of smoothness of gold alloys according to polishing time and polishing materials were compared. The following results were obtained : 1. When the amount of loss of gold alloys polished with 3 kinds of brown rubber point was compared, Alphalex brown point had the most amount of alloy loss, followed in decreasing order by Shofu brown point and Eveflex brown point. There was statistically significant difference in the amount of alloy loss according to polishing materials. 2. When the amount of loss of gold alloys polished with 5 kinds of green rubber point was compared, Shofu green point had the most amount of alloy loss, followed in decreasing order by Alphaflex green point, Dedeco green clasp polisher, and Eveflex green point. There was statistically significant difference in the amount of alloy loss according to polishing materials except Alphaflex green point and Dedeco green clasp polisher. 3. When the amount of loss of gold alloys polished with all kinds of rubber point was compared, there was no significant difference in Eveflex brown point, Alphaflex green point, and Dedeco green clasp polisher. 4. When average amount of alloy loss per 1 revolution by polishing materials was compared, Alphalex brown point had the greatest value as $0.329{mu}m$ and Shofu supergreen point had the lowest value as $0.022{mu}m$. 5. When the degree of sureface smoothness of gold alloy polished with 3 kinds of brown rubber point was compared, In Alphalex brown point surface roughness was completely lost after 20 seconds polishing time, in Shofu brown point 30 seconds, in Eveflex brown point 40 seconds. But in every gold alloys fine scratch formed by rubber points was observed. Based on the results of this study, as rubber polishing materials used in polishing of dental casting restoration after clinical adjustment influenced on the tightness of occlusal or proximal contact, we should make dental casting restoration with minimum error through careful laboratory procedure and form very smooth surface of restoration with tripoli and rouge after use of silicone polishing materials.