This article investigated the microstructure and electrochemical corrosion properties of electron beam 3D printed Ti6Al4V alloy and the relationship between both. The results indicate that the original β columns that grow along epitaxial direction, parallel to the molding direction (XOZ plane), are mainly composed of columnar grain boundary α phase and cluster α growing along the grain boundary and basketweave microstructure inside the grain. The αsheet orientation of the basket structure is different, and the small rodlike β phase is located between the α sheets. The corrosion resistance of each molding surface were studied by measuring the dynamic polarization curve and electrochemical impedance spectroscopy of the alloy in hydrochloric acid solution. Compared with XOY surface, XOZ surface shows better corrosion resistance, this difference in performance is closely related to the microstructure of the alloy, which mainly reflected in the terms of the content of β phase by means of OM, SEM and TEM. The higher β phase content of the XOZ surface has the better corrosion resistance. Therefore, by controlling the molding process to obtain a high content of β phase, the corrosion resistance of the alloy can be improved. In addition, the application surface of the electron beam 3D printing Ti-6Al-4V alloy should be reasonably selected in the acidic solution to obtain better corrosion resistance.