Abstract: Based on the previous high?accurate new oil?water relative permeability studies, this paper established a new relationship between oil?water relative permeability ratio and water saturation. Combined with Leverett function and Welge equation, it deduces the analytical formulae for waterflood frontal water saturation, waterflood post?frontal average water saturation, water?breakthrough average water saturation and oil displacement efficiency, in order to calculate waterflooding indices and automatically draw relative the classic curves.The case study from Qiuling oilfield shows that this analytical method is not only used to calculate the waterflood frontal saturation and other indices, but also draw such classic curves as the oil displacement efficiency vs. injected fluid volumes, water cut vs. injected fluid volumes, etc