Using graphite, copper and tungsten as strengthening electrodes, the surface of TC4 titanium alloy is strengthened with powder-mixed near-dry ElectricalDischarge Machine (EDM) under positive and negative polarity, respectively. The effects of different electrodes and polarity on microstructure and properties of the strengthened layer were analyzed. The results show that the thin dendritic structure and petal shape are obtained by negative processing of graphite electrode, and the cake structure is obtained by negative polarity processing of copper electrode and tungsten electrode, and the superposition layer is obvious. The hardness of the strengthening layer is much higher than that of the base material, including the negative processing of graphite electrode and tungsten electrode, and the strengthening of copper electrode with positive polarity processing. The hardness is over HV1 000, the highest is about 3.4 times of the matrix.