Abstract: Gas accelerator pump usually called gas-lift jet pump, was developed combined with merits of gas-lift technique and jet pump technique, and widely used in domestic and foreign oilfield, but there is little reports on lifting efficiency and two-phase flow. Study on the principles of gas accelerator and lifting theories, in the view of energy, considering the pressure, heat, potential, expanding and kinetic energy theory, a lifting efficiency model of gas accelerator was developed, applications indicate that gas-lift efficiency can be greatly enhanced by gas accelerator, and compared with results acquired by non-slippage pressure gradient method, Hagedorn-Brown method, Schmidt method and experiment data, indicates that pressure losing of two-phase flow was greatly reduced.