Oil-water two-phase flow widely exists and its measurement is of significance in oil well logging, oil transportations and etc. One of the techniques in common use in oil-water two-phase flow rate measurement is the Differential Pressure (DP) meters combining a theoretic model connecting the mass flow rate of the mixture with the differential pressures generated by the throttling element installed inside the pipeline. Though a number of publications focus on DP meters in measuring gas-water two-phase flows or wet gas, the existing models are still not very compatible in oil-water two-phase flow. In this work, a series of oil-water two-phase flow experiments were conducted in a horizontal pipe of 50mm diameter and the flow rate was measured by a V-cone meter with a diameter ratio of 0.65. Available correlations of DP meters developed from gas-water flow are studied and compared with the measured data from the V-cone meter. A modified correlation is proposed based on the influence of viscosity of oil upon the differential pressure model and three-dimensional Computerized Fluid Dynamic (CFD) simulations. The results have shown that the proposed method achieves better accuracy in oil-water two-phase flow rate measurement than other DP correlations, and it can be extended to other oil-water flow conditions by adjusting the tuning factor.