Abstract: Using CO2 and CH4 respectively to generate hydrate based on a special designed apparatus，the paper discussed the formation of hydrate in two experiments． Each experiment collected hydrate crystals at three different reaction periods． The ion concentration of Na + ，Mg2 + ，K + ，Ca2 + ，B3 + in the hydrate was dectected． The result showed that: Ｒemoval efficiency of each dissolved mineral strongly depends on the ionic size and charge during the hydrate process of CH4 ，showing a linear correlation． By the use of CO2 as the hydrate forming gas，the carbonate ions caused the precipitation of calcium ions in the form of CaCO3 ． So the calcium ion ( Ca2 + ) did not show the linear correlation． The study illustrated a more comprehensive ion rejection mechanism of dissolved minerals by the process of gas hydrate． Compared with the traditional methods in reverse osmosis，hydrate method had good advantage of boron removal．