To explore the mechanisms underlying the compaction performance of sulfate saline soil, a series of light compaction tests is conducted on sulfate saline soils under various mixing conditions. The testing results show that the effect of salt content on the maximum dry density and the optimum moisture content of sulfate saline soil is complex; and it depends on the three states of sodium sulfate (sodium sulfate solution, anhydrous sodium sulfate and sodium sulfate decahydrate) and the relative amount of these three states of sodium sulfate. Both the maximum dry density and the optimum moisture content are inversely correlated to the relative amount of different states of sodium sulfate in the soil. The effects of the original moisture content and the curing times on the compaction are related to the salt content. The effect is trivial when the salt content is low (e.g. 1.5%), and very significant when the salt content is high (e.g. 5.0%). During the drying process, sulfate saline soil shows a false drying phenomenon. These experimental results provide a reference for evaluating the compaction characteristics and the degree of compaction of sulfate saline soils.