Abstract: Through user defined function and numerical simulation method, the pressure drop of foam flowing in coiled tubing was studied. The simulated results were compared with that gained by empirical correlation. For foam flowing in straight tubing section, the simulated pressure drop was higher than the calculated because of the effect of acceleration pressure drop and the consideration of velocity profile variation. For foam flowing in spiral section, the physical properties of the compressed foam varied with the variation of pressure, so the velocity profile and density profile would be different at the same section under different exit pressure. The velocity profiles were asymmetry due to centrifugal force. The exit pressure, gas injection rate and curvature obviously influenced the pressure drop. For designing the hydraulic parameters of foam drilling with coiled tubing, with the permission of experiments, the injection pressure should be enhanced as largely as possible to decrease pressure drop of foam flowing in the spiral section.