Abstract: There is a large number of coal fly ash in our country，and it is a kind of available resources.Physical and chemical properties of coal fly ash were introduced.Role of soil improvement was summarized，such as improving soil physical properties，increasing soil nutrients，affecting soil biological activity，controling saline alkali land，and repairing and controling heavy metal pollution.Coal fly ash can also be used for land reclamation project to change soil structure and increase productivity of soil.It was a high quality completed land engineering guarantee.However，before use of coal fly ash，it still needs pretreatment and detection of nature.