The invention relates to an electrolytic milling-grinding machining tool cathode with efficiency and precision and an electrolytic milling-grinding method, and belongs to the field of electrolytic milling-grinding composite machining. According to the electrolytic milling-grinding machining tool cathode and the electrolytic milling-grinding method, a plurality of arc-shaped grooves at equal intervals are formed in the lower end of the side wall of the tool cathode, the side walls of the grooves are insulated, and diamond abrasive particles are inlaid in the wall surfaces of the portions, except for the grooves, of the side wall of a cathode base body through a resin binder, so that electrochemical anodic dissolution only exists in the surfaces of the portions, opposite to the grooves, of aworkpiece, at the moment, the depths of the grooves become a part of a machining gap, accordingly the contact depth between the diamond abrasive particles in the portions, except for the grooves, ofthe side wall of the cathode base body and the machining surface of the workpiece is increased, then the grinding effect of the diamond abrasive particles on the workpiece in the electrolytic milling-grinding process is enhanced, and the precision and the surface quality of the electrolytic milling-grinding machining can be improved; and moreover, compared with the electrolytic milling-grinding finish machining under the low current density in the past, the tool cathode can adopt higher current density, and the machining efficiency can be improved.