The geopolymer gel, which can be linked with other minerals in geopolymer, is the source of material strength. In this experiment, geopolymer gel was prepared by the aluminosilicate sol obtained after the extraction of potassium from slate with the addition of NaOH at 60℃. XRD, SEM, IR and NMR wereused to investigate the structure of the gel at different solidification time spans. The result shows that there is no new crystal phase produced during the formation of the gel, implying that the gel is amorphous. It is also shown that with the change of the solidification time, the［SiO4］4- tetrahedron of the gel depolymerizes at first and polymerizes afterwards. The gel forms a compact mass after polymerization.