Basic　and　applying　research　works　on　mineral　fast　ion　conductor　which　lasting　more　than　ten　years　by　our　group　are　reviewed.　Nasicon　type　FIC　was　prepared　by　high　temperature　solid　phase　reaction,　used　clay　mineral　as　starting　material.　Three　factors　affect　conductivity:　polarization　effect,　comparative　size　between　passage　and　migrating　ion,　and　filling　amount　of　dopant　ion.　Reformed　montmorillonite　(thereafter　refered　to　as　mont.)　was　produced　by　ion　exchange　method　and　molecular　substition　method.　XRD　data　proves　that　the　lattice　of　reformed　mont.　remain　the　same　as　natural　mont.　Thermal　analysis　data　and　conductivity　data　show:　It　is　water　which　is　absorbed　in　surface　of　mont.　that　enhanced　migration　rate　of　conducting　ion,　not　water　resided　between　two　layer　of　mont.　Practice　of　solid　magnesium　cell　using　mont.　as　electrolyte　show:　it　can　serves　as　power　source　for　microelectronic　device.