Abstract: Reservior fluids properties identification plays an important role in production, especially for offshore oil fields which usually are lack of well logging data. The difference between water saturation and the irreducible water saturation calculated by logging data is generally used to identify reservoir fluids properties. In fact, whether the reservoir produces water or not depends not only on the water saturation and the irreducible water saturation, but also on the relative permeability and viscosity of fluid in reservoirs. In this paper, the method of using water content calculated by logging data and petrophysics to evaluate the output ratio of oil and water of the reservoir is proved to be effective. This method has a great significance to identify the fluid property of the reservoir and can lay a solid foundation for oilfield completion and production.