Objective To investigate the influences of W-EDM process on the surface quality of materials,analyze the mechanical properties of the machined surface. Methods The wire electrical discharge machining was used to conduct the surface cutting test of 304 stainless steel. The profilometer, scanning electron microscope (SEM), electron microscope and nanoindentation were used to examine the variation pattern of surface roughness and surface micro-morphology and obtain the micro and nano-hardness curve of electric discharge machining (EDM). The orthogonal experiment was designed to obtain the optimal parameters. Results The machining pulse width length and the peak current of austenitic stainless steel processing had a significant effect on the formation mechanism of surface morphology. The surface roughness was greatly influenced by electrical parameters. The surface and the subsurface tissues were mainly composed of the layer of plastic deformation and the layers of tempered multiphase. Changes were great in the thickness and the nano-hardness due to the influence of the electrical parameters. Conclusion Electrical parameters by their effects on the surface quality in order were pulse width, peak current, and discharge interval. In order to obtain the optimum machining surface layer, priority should be given to select pulse width 16 μs, discharge interval 96 μs, peak current of 1. 5 A as the processing parameters. Single pulse energy exhibited a nearly linear association with thickness and nano-hardness of the processed layer.