Abstract: In the development period with ultra -high water cut,water absorption in plane, interbeds and in -layers are sevearly unbalanced due to reservoir inhomogeneity.How to improve iulection profile,raise sweep effciency of iulected water and improve waterflood recovery factor,are the major problems that have to be settled urgently in late period of development. This paper analyzes the changing trend of injection profile over the years in Zhongyuan oilfield, discusses the main influential factors of injection profile both in theory and in practice, and presents the effective way of improving injection profile and the direction to further tap the production potential of the field.