Abstract: A simplified interelectrode flow model of wirecut electrical discharge machine was proposed. The effect of the plate length, velocity and gap width respectively on pressuredifference flow and shear flow was investigated. The compound gap flow formed by combining the pressuredifference flow and shear flow was analyzed. By adding coaxial nozzle and adopting high energy, a test was done to compare the cutting efficiency and surface quality of the single casting fluid supply dominated by shear flow with that of the combination fluid supply supplemented by highpressure spray liquid. The results show that compared with the single casting fluid supply, the gap condition of the combination fluid supply is improved obviously: the maximum cutting efficiency nearly reaches 220 mm2/min, increases by 20% and little surface burns are got, which verifies the effect of the composition of pressuredifference flow and shear flow.