Abstract: Electro-discharge dressing of super-abrasive grinding wheel was limited by the discharge gap. It was difficult to meet the requirements of the dressing of coarse-grained wheels under traditional dielectric conditions. Based on the mechanism of electrical discharge machining (EDM) with powder mixed dielectric, a method of electrical discharge dressing (EDD) with powder mixed dielectric was presented. A comparative study on the discharge gap of compressed air, deionized water mist and powder mixed deionized water mist with different discharge parameters was carried out. Furthermore, the experiment of dressing and grinding of diamond wheel was carried out. The results show that the EDD with powder mixed dielectric has larger discharge gap, which can improve the dressing efficiency of the coarse-grained bronze bonded diamond wheel, and optimize the surface morphology, abrasive protrusion and grinding performance of the wheel after dressing. The efficiency of EDD in powder mixed dielectric is increased by 28.2%~50.0% compared with the other two kinds of dielectric under the optimal parameters of open circuit voltage of 90 V, peak current of 13.33 A and duty of 50%. The addition of SiO₂ powder makes the distribution of Si element on the surface of grinding wheel more uniform and the content higher, thus improving its wear resistance.