According to the formers' study of theory and experiment, to analyze the mechanical properties on compacting effect of lime compaction piles. The effects of collapsible loess reinforced by the lime pile have been analyzed. The theory of collapsible loess reinforced by lime pile has made useful exploration. Through the round hole expansion theory to lime piles under expansion compacting process, the elastic-plastic solution on compacting effect of lime compaction piles has been solved. The effective radius of expansion and the law of stress change between the piles can also be determined. Finally using the finite element method to verify the proposed method, and the results show that the proposed method is effective and can provide theoretical basis and guidance for the similar projects.