Abstract: Based on Buckley?Leverett theory of water displacing oil in non?piston, Welge’s average water saturation equation and Efros’ experimental results, the water cut vs recovery efficiency curve, the water drive characteristic curve and the water cut rising curve corresponding to the classical water displacing oil theories are derived in this paper. Although the oil?water two?phase relative permeability function is not introduced in the process of derivation, the cumulative oil production vs cumulative liquid production can also be given from the theoretical and experimental research results, which has a big difference with previous derivation methods for water drive type curves. Through field application, the effect is very good and worthy of popularization and application