Because of low fusion heat and vaporization heat of aluminum, when WEDM is used to machine aluminum alloy, melting reaction is easy to produce, machined surface is rough,the electrical erosion is adhered on the molybdenum wire,the conductive block is early weared,and abnormal spark discharge is generated between molybdenum wire and workpiece which cuts out small grooves on the surface of the conductive block,causing the phenomena of climping wire, broken wire.The measures and methods to improve the stability and the quality of cutting surface were obtained by improving the cutting process and experiment.