A proper degree of compactness is very important for reducing the dilatancy and collapsibility of sulfate saline soil foundation. To investigate the compaction characteristics

the microstructure characteristics of sodium sulfate saline soil with different preparation conditions were investigated using scanning electron microscope (SEM). It is found that the compaction characteristics and microstructure characteristics of sodium sulfate saline soil after compaction are related to the state of sodium sulfate in soil. As sodium sulfate solution possesses lubrication

the compaction characteristic of sodium sulfate saline soil is significantly improved as salt content increases. After the soil is compacted

the soil aggregates are mostly thin layers with smooth surface

and the soil has a rhyotaxitic mosaic structure. However

sodium sulfate decahydrate acts like a scaffold in the soil

the increase of salt content reduces significantly the compaction characteristics of sodium sulfate saline soil. After compaction

the soil aggregates are tiny and round

and the soil has a net-like open structure. The effect of sample pretreatment method and curing time on the compactness of sodium sulfate saline soil are analyzed

and the evaluation method for the compactness is suggested.