Abstract: This paper presents a case study of an impact technology applied in a highway embankment on collapsible loess.Based on soil test and settlement observation,the authors assessed physical and mechanical parameters of subgrade(collapsibility,dry density,void ratio,compression modulus,settlement and other parameters) and their changes with the depth of soil strata and the pressing number before and after the impact compaction..The results show that the physical and mechnical properties of soil were improved greatly by the compaction.The overall strength of highway subgrade can be enhanced.It is concluded that the impact compaction technology is effective and practical for treatment of collapsible loess subgrade.