In order to improve the bearing capacity of concrete filling pile,based on the theory of concrete compensating shrinkage,we add an appropriate amount of HCSA expansive agent in concrete filling piles.This paper analyzes the influence of different dosages of HCSA on the expansive property of cement mortar and on the strength and volume deformation of concrete,and applies it in the project.According to the result,HCSA expansive agent has faster expansion rate and greater expansion ability,the bearing capacity of pile increases by 34.3% when the HCSA content is 15%,the settlement amount of friction pile using expansive concrete technology is only 36%～44% of ordinary concrete pile,the quality of concrete filling piles is improved.