Electrical discharge machining(EDM) keyhole exists some problems such as low machining efficiency due to low discharge efficiency of electro erosion products,secondary discharge phenomenon due to discharge of electro erosion products and influence on machining accuracy.The cavitation effect and pumping effect generated by ultrasonic vibration in the working fluid can greatly improve the chip discharge and deionization ability of EDM,thus the occurrence of the above problems is reduced to a large extent.A set of working fluid ultrasonic vibration assisted EDM keyhole machining device was designed,which mainly included spindle system,micro-three-dimensional motion platform,ultrasonic vibration working liquid groove and data acquisition system.The spindle system included NSK electric spindle,power transmission structure and tool electrode clamping structure,which could realize high-speed rotation of tool electrode.The EDM keyhole machining control system was developed based on LabVIEW,which included initialization module,rough positioning module,constant voltage tool setting module,real-time voltage subsection control machining module and real-time display module.The experimental study of working fluid ultrasonic vibration assisted EDM was carried out.The experimental results show that the material removal rate and electrode loss rate tend to increase with the increase of EDM voltage.