Abstract: Bayer-process red mud has special physical and hydraulic properties, can be used for subgrade filling through improved treatment. Lime,cement,phosphogypsum and composite modified materials are selected for chemical improvement of red mud, and the effect of different modified materials on the compaction characteristics of red mud is analyzed. The results shows that different materials have different characteristics in improving red mud compaction, and the optimum moisture content and maximum dry density of red mud improved by each material show different increasing and decreasing trends with the change of dosage. It provides a reference for the selection of improvement methods and engineering application of Bayer red mud.