LiNO3 addition to cement was examined to prevent hydrogen gas generation from metallic aluminum in dry active wastes during waste solidification and under circumstances of underground water penetration into the land disposal site. And its reaction mechanism was identified by some chemical analyses. The volume of the hydrogen gas generation with LiNO3 addition was 10% as much as that without LiNO3, by formation of the insoluble Li-Al preservation film on aluminum. After the land disposal of waste forms, LiNO3 would be expected to be effective to prevent aluminum corrosion as long as the cement forms keep their alkaline character, and when it became ineffective, the circumstances around the waste forms can be made less corrosive for aluminum. The aluminum corrosion at that time would be as much as 10% of that without LiNO3 addition.