Abstract: The reservoirs in Dagang south oilfield is multi-layer and conflict between layers.In order to improve injection efficiency and production degree of low permeability reservoir,and realize multistage separate injection,the plug-in surface separated injection technology and concentric dual-barrel separated injection technology are developed and applied in five wells in south-oilfield,which prove that the pilot test is effective.The results of test shows that the matching technical level of separated injection is improved and some difficult technology problems of deep well,high injection pressure,condensed oil,scaling and great difficulty of pulling and running for water injection allocation can be solved by using the surface multistage separated injection technology.