The relative permeability curve is the basis for studying the two-phase flow in reservoir. It is an indispensable and important data for numerical simulation and dynamic analysis of oilfields.At present, the researches on the relative permeability both domestic and overseas were mainlygiven priority tothe methods of dealing with the relative permeability data or the application of the relative permeability curve, the paper about the experimental methods was likely rare.For the moment, the most immediate method for obtaining the data of relative permeability is the experimental of non-steady-state. This method is simple to operate with short time and has universal applicability. However, since the experimental points of non-steady state method are often concentrated after oil and water both coming out, resulting in the data of the oil-water front are less. The impact is relatively small for the heavy oilfield, but for medium-light oil fields, it cannot be ignored.The viscosity ratio of water-oil in medium-light oil field is relatively high, the fractional flow rate curve has a stronger concave shape.Compared with the heavy oilfield, those oilfields have a longer water free production or lower water cut periods with same physical conditions and development methods. The non-steady state method application in medium-light oil field may cause deviation, resulting in difficulties to accurately understand the law of water rising.In this paper, the steady-state and unsteady state method were used to obtain the relative permeability data.The results show that the two methods are quite different when the viscosity of the crude oil in the formation is less than 6 mpa·s.Steady state method should be adopted. When the viscosity is higher than 6 mpa. s, the difference can be ignored and non-steady state method should be adopted instead.Based on the above-mentioned interpretation, the research on the main controlling factors influencing the relative permeability of medium-light oil fields was carried out.The results show that the viscosity of non-wetting phase, the characteristics of sedimentary facies, the temperature and wettability played important role on the phase-permeability curve and the law of water rising.This article dedicates to give a complete description on relative permeability curve in medium-light oil field, which is of great significance for numerical simulation and dynamic analysis.