The invention discloses a method for directly preparing a supported metal Co catalyst. In the provided method, cobalt nitrate, sugar and silicon dioxide are taken as the raw materials, and a vacuum impregnation technology and a high temperature carbonization method are adopted to prepare the supported metal Co catalyst. In an inert gas atmosphere, sugar is decomposed at a high temperature to generate reducing substances, the reducing substances reduce the cobalt compounds, the supported metal Co catalyst is prepared directly, while in the conventional Fischer-Tropsch synthesis, the catalyst should be reduced into metal Co by hydrogen gas at a high temperature, in the provided preparation method, the hydrogen gas reduction step is eliminated, the provided method is simple, the conditions are controllable, the catalyst is directly applied to Fischer-Tropsch synthesis, and the CO conversion rate is prominently improved, compared with the CO conversion rate in the presence of a Co/silicon dioxide catalyst, which is prepared by a conventional impregnation method.