The effect of mixed powder ultrasonic vibration on the surface structure and the mechanical properties of Ti-6Al-4V in Electro-Discharge Machining (EDM) were studied. The surface roughness, the residual stress and the micro hardness of Ti-6Al-4V simples machined by conventional EDM, powder mixed EDM (PMEDM) and combination process of powder mixed EDM with ultrasonic machining (PMEDM+USM) were measured, respectively. The recast layers and the surface cracks of samples machined by EDM, PMEDM and PMEDM+USM were observed by SEM, the quantitative analysis of each element of samples machined by PMEDM and PMEDM+USM was performed by energy spectrum analyzer. The effect mechanism of added Al and SiC powder in kerosene and ultrasonic vibration of electrode on the surface structure and the mechanical properties of Ti-6Al-4V machined by PMEDM+USM were also discussed. The results show that the surface structure and the mechanical properties of Ti-6Al-4V are improved by PMEDM+USM. With under the effects of the electrode ultrasonic vibration and SiC added in kerosene, the surface roughness decreases by Ra 0.5 μm, the recast layer reduces by 40 μm, the surface residual stress decreases by 50 MPa, and the surface hardness increases from 7650 to 9870 MPa than PMEDM