ZnO　varistor　is　a　kind　of　semiconducting　oxides,　which　consists　of　the　N-P　bicrystal　structure　of　crystal　grains　and　grain　boundaries.　ZnO　varistors　of　intermediate　and　low　voltages　are　still　under　investigation.　In　this　paper　the　ZnO　varistor　of　intermediate　and　low　voltage,　which　was　prepared　by　adding　crystal　seeds,　has　been　discussed　and　its　microstructure　has　been　studied　by　SEM.　The　conducting　mechanism　was　also　discussed.