Mechanical energy loss is usually considered to be generated from frictional pressure drop in pipe flow. An analytical equation was derived from hydrodynamic model to estimate the mechanical energy loss in intermittent two-phase flow. This equation indicates that only part of energy loss is generated from frictional pressure drop in inclined and vertical intermittent flows. Experiments were conducted in a gas-liquid pipeline to investigate the different effects of drag-reducing polymer (DRP) on the mechanical energy losses of turbulent intermittent flows in pipes. The inside diameter of the pipeline is 0.04 m. Whether or not DRP is used, the results show that the mechanical energy loss is highest in the vertical case and is lowest in the horizontal case among horizontal, inclined, and vertical intermittent flows. The energy loss reduction induced by DRP in horizontal intermittent flow is greater than the one in either vertical or inclined intermittent flow.