The multilayer DLC coating was successfully fabricated on the surface of 304L stainless steel and silicon wafers by unbalanced magnetron sputtering technology. The tribocorrosion tests were carried out in a triboelectrochemical cell using a ball-on-plate tribometer integrated with a potentiostat for electrochemical control. Results showed that the open circuit potential (OCP) and corrosion potential (Ecorr) of 304L substrate presented great fluctuation. However, the OCP and Ecorr values of the multilayer DLC coating remained relatively stable during these tests. Meanwhile, the friction coefficient decreased and the wear-loss increased with the polarization potential increased from −1 to 0.5V. In addition, with an increase in polarization potential, the mechanical wear decreased obviously and the corrosion-induced wear gradually occupied a dominant position for 304L substrate, nevertheless, the mainly volume loss of the multilayer DLC coating was mainly attributed to pure mechanical wear. Thus, the tribocorrosion resistance of the multilayer DLC coating was superior to 304L substrate in seawater, manifesting its good potential as a protective material for marine industry.