<p>A new method of ultrasonic vibration-assisted powder-mixed near-dry multi-dielectrics electrical discharge surface strengthening is proposed in this paper It produces a hard and firm strengthened layer on the surface of TC4 alloy. The changes in microstructure and properties of the strengthened layer of titanium alloy strengthened by EDM before and after adding the ultrasonic assistant device were compared and analyzed. Revealed the influence mechanism of ultrasound on the formation of the strengthening phase. The results showed that the compound addition of ultrasonic vibration and C+B4C+Al powder caused no voids and globules in the strengthened layer, and the surface of the strengthened layer was denser and flatter. The XRD results showed that the ultrasonic vibration promoted the chemical reaction between the powders, electrodes, and base materials, resulting in the disappearance of the B4C phase deposited in the strengthened layer. It is worth mentioning that a variety of new strengthening phases such as CuAl2 and Al3Ti phases were generated in the strengthened layer, realizing hybrid strengthening of the strengthening layer, and resulting in a maximum microhardness enhancement to 1373 HV of the strengthened layer.</p>