The invention discloses a root key type anchor cable and a method for grouting in anchor holes. The anchor cable comprises an anchor table, an anchorage device, a plurality of pressure bearing mechanisms and a plurality of rib bodies, wherein the anchorage device is fixedly connected with the anchor table to form an outer anchorage section; after the pressure bearing mechanisms are serially connected with the rib bodies, fixed ends of the rib bodies are then connected to the outer anchorage section in parallel respectively; hoisting ends of the rib bodies are used for hoisting the pressure bearing mechanisms; a plurality of root keys capable of extending in rock and earth masses of the anchor holes are arranged on the pressure bearing mechanisms outwards in the radial direction; each through hole is formed in the center of the corresponding pressure bearing mechanism; circle centers of the various through holes are positioned on the same straight line; diameters of the various through holes are the same; a penetrating hole is reserved in the outer anchorage section; the circle center of the penetrating hole and the circle centers of the various through holes are positioned on the same straight line; the diameter of the penetrating hole is the same with the diameters of the various through holes; a grouting pipe penetrates through the penetrating hole and the various through holes; and the grouting pipe, the pressure bearing mechanisms and the outer anchorage section form a sliding pair. The method for grouting in the anchor holes is implemented on the basis of the anchor cable. By the anchor cable and the method, the anchorage effect of the anchor cable can be improved effectively.