A method of using auxiliary electric current to restrain the stray corrosion of EDM of t itanium alloy machined in water is proposed. In the method， an auxiliary power supply is u sed to provide enough cathode current to make the metal interface electronegativ e， as a result of which， the stray corrosion is inhibited. The m echanism of stray corrosion and how to restrain it by auxiliary electric current are studied. The surfaces of titanium alloy machined before and after adopting auxiliary electric current are tested by several means， such as electric field simulation analysis， electrical discharge machining tests， surface morphology an d component analysis， and so on. The experimental results show that the auxili ary electric current can efficiently eliminate the stray corrosion of EDM of t itanium alloy machined in water.