Abstract: Taking white oil and water as experimental medium, an oil-water two-phase experiment is carried out to measure water holdup in a transparent glass tube with the length of 9.2 m and inner diameter of 60 mm. The paper analyzes the influences of inlet water cut, mixture flow rate, oil viscosity and tube dip on water holdup, and compares the precision of the results predicted by 4 commonly-used water holdup prediction models, i.e. drift model, slipping model, Nicholas-Witterholt model and standard Taitel model, among which relatively good results can be gained from Nicholas-Witterholt model. Considering the influences of tube dip and inlet water cut and so on, Nicholas-Witterholt model is modified and Nicholas-Witterholt II model is obtained. The experimental data are substituted into Nicholas-Witterholt II model and it is found that the error of the result predicted by the modified model is about 10%, indicating that the modified model has good general applicability.