Abstract: In order to reduce alkali and increase harmless utilization of red mud，phosphorus gypsum and CaCO3 were used as dealkalization agents.Results showed that oscillation of 0.5 h，a very short time could make the pH and EC values stable. Dealkalization efficiency neither depended directly on the ratio between dealkalization agent and red mud，nor the dealkalization time.Considering the dealkalization effeciency and economic cost，the mass ratio between red mud and phosphogypsum was 1∶ 0.4，and red mud and CaCO3 was 1∶ 0.2.After adding the calcium compounds，they reacted with red mud，thus more combined alkali was replaced into free alkali so as to be removed.

Key words: red mud, dealkalization, phosphogypsum, CaCO3