Abstract: High-pressure oedometer tests were conducted on soils pre-densified with the same amount of verticaldeformation formed by static load and impact load under confined compression conditions． Compaction curves, preconsolidation pressures and compression indexes of same pre-densification deformation soil formed in different waywere comparatively investigated． The results showed that compression indexes of same pre-densification soil were closeand irrelevant to the cause of pre-densification; compression curves and preconsolidation pressures were varied with soiltypes． For lower saturated soils, compression curves and preconsolidation pressures after compression were only relevantto pre-densification deformation amounts and irrelevant to the cause of pre-densification in same pre-densificationcondition; for nearly saturated soils, over-consolidated states were formed due to static loads and preconsolidationpressures increased with the amounts of pre-deformation; but over-consolidation states formed by impact load were notobviouse, preconsolidation pressures were irrelevant to pre-densification deformation formed by impact load．