Ti6Al4V specimens prepared by electron beam selective melting were heat-treated for 1, 3, 5, 7, and 9 h, and the Tafel and electrochemical impedance spectroscopy experiments were conducted to discuss the behavior and mechanism of electrochemical corrosion. Through the modification mechanism analysis of corrosion performance, it is found that the more the <111> crystal orientations, the greater the proportion of small-angle grain boundaries, the larger the grain diameter, and the better the corrosion resistance. The specimen after heat treatment for 5 h has the most uniform <111> crystal orientations. The proportion of small-angle grain boundaries is the highest of 56.2%, the grain intercept is 5.252 μm, and the corrosion resistance is optimal with corrosion current of 0.037 μA/cm².