Abstract: This paper proposes a new method to improve the surface performance of workpiece,which can synthesize TiN coating on the surface of titanium alloy TC4 by using flexible titanium electrode. During the whole processing the spark discharge occurs between the surface of titanium alloy TC4 and flexible titanium electrode. At the same time nitrogen gas was poured into processing area via the titanium electrode internal tunnels,and TiN coating was produced by using the energy of electric spark discharge. The layer's surface hardness,microstructure and chemical compositions were tested with microhardness tester, SEM and XRD,respectively. The result showed that strengthened homogeneous and continuous TiN coating was obtained in the coating layer. Moreover,the layer's thickness reaches more than 1 mm and its microhardness is up to 1859. 6HV. Discharge craters on the surface of coating is big and bright and have scraping marks,so it can be known that flexible titanium electrode has stronger scraping and grinding effect on TiN coating. In addition, TiN coating interinfiltrate with matrix,forming metallurgic bonding.