This paper with the bush forest,needle leaf forest and rich leaf forest of Qilian mountains 3 kinds of forest land is research material,discuss the different type of forest land as soil reason melts,the influence of nature and the selfcontrol function of source of water,show as a result: Soil porosity,granule structure and physicalness glue grain content is bush forest > needle leaf forest > rich leaf forest,soil unit weight and physicalness sand grain content are bush forest < needle leaf forest < rich leaf forest;Soil organic matter,whole N,N of quick result,P of quick result,K of quick result and CEC is bush forest > needle leaf forest > rich leaf forest,and CaCO_3,pH,completely salt content is bush forest < needle leaf forest < rich leaf forest;Soil water layer thickness,natural water content,saturation reservoir storage and woollen pipe reservoir storage,not woollen pipe reservoir storage,store water quantity is bush forest > needle leaf forest > rich leaf forest;Withered fall thing accumulation thickness,withered fall thing accumulation dry quality,hold water quantity,biggest hold water rate is bush forest > needle leaf forest > rich leaf forest.Bush forest plant kind is rich,closing degree big,withered fall thing accumulation quantity much,the self-control function of source of water is strong.