The age of cobalt-rich crusts from the Magellan Seamount in the western Pacific has been first approached by using the method of biostratigraphic dating. The subsamples collected from the positions at 20, 35, 58, 62 and 75 mm from top to bottom in a crust 97 mm thick were studied. Special calcareous foraminiferal prints of Discoaster multiradiatus, Discoaster elegans, Discoaster barbadiensis, Tribrachiatus arthostylus etc. of the early Eocene were found at 62 mm. It is thus concluded that the age of cobalt-rich crusts in this area can be traced back into the Eocene or even earlier. In addition, the authors have made a correlation of the present dating with that of crusts from the Central Pacific and present a discussion on its geological significance.