The purpose of this study is to investigate the characteristics of the compositions and phases of amalgam alloys and amalgams by using EMPA and X-ray diffractometer. Each specimen was made from Caulk Fine Cut Clow copper lathe cut amalgam), Caulk Spherical (low copper spherical amalgam), Tytin (high copper unicorn position amalgam), Dispersally (high copper admixed amalgam) and Valiant (Palladium enriched amalgam). For preparing amalgam alloys, Tytin and Valiant were used as powder forms and the others were used as tablet forms after being polished with polishing machine. For preparing amalgams, each amalgam alloy and Hg were measured, and triturated by mechanical amalgamater according to user's instructions. After triturating, the triturated mass was inserted to cylindrical metal mold and simultaneously adapted by cylindrical condenser with same diameter and condensed by Instron universal testing machine with 80kg pressure & 1mm/min speed. Each specimen was removed from the metal mold and stored at room temperature for a week. The specimen was polished with the same polishing machine for amalgam alloy. For observation of microstructure and analysis of composition of amalgam alloys and amalgams, EMPA was used to get secondary electron images, backscattered images and characteristic X-ray images of Ag, Sn, Cu, Zn, Hg. To analyze compositions of amalgam alloys and amalgams, X-ray diffractometer was used. Amalgam alloys were scanned at the range of 2${\theta}$ of 30-$85^{\circ}$ and the speed of $4^{\circ}$/min with Cuka line and amalgams were scanned at the range of 2${\theta}$ of 28-$44^{\circ}$ and the speed of $4^{\circ}$/min with Cuka line. By comparing obtained d(distance between surfaces) and d of expected phases and atoms in amalgam alloys and amalgams in ASTM card, phases and atoms were identified. The results were as follows, 1. In Caulk Fine Cut amalgam alloy typical ${\gamma}$ phase was shown, and in amalgam, ${\gamma}$, ${\gamma}_1$ and ${\gamma}_2$ phases were observed. 2. In Caulk Spherical amalgam alloy ${\gamma}$, Ag, Cu and $\varepsilon$ phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, ${\gamma}_2$ and $\eta$ phases were observed. 3. In Tytin amalgam alloy ${\gamma}$, Cu and $\varepsilon$ phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, $\eta$ and $\varepsilon$ phases were observed. 4. In Dispersalloy ${\gamma}$, Ag, Cu and $\varepsilon$ phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, $\eta$ and $\varepsilon$ phases were observed. 5. In Valiant alloy ${\gamma}$, Cu and e phases were shown, and in amalgam ${\gamma}$, ${\gamma}_1$, $\eta$ and $\varepsilon$ phases were observed.