The invention discloses a catalyst manufactured by embedding ruthenium in mesoporous polymer-silica, a preparation method thereof and application thereof. The catalyst is characterized in that; the catalyst is synthesized in one step by using the mesoporous polymer-silica as a carrier and ruthenium trichloride as an active component precursor and adopting a solvent volatilization self-assembly (EISA). The preparation method comprises the steps of solvent volatilization self-assembly, high-temperature thermal polymerization and vacuum calcination. The catalyst is used for the hydrogenation of benzaldehyde and is characterized in that: the activation of the catalyst and the hydrogenation are performed at room temperature and under medium hydrogen pressure. Compared with the prior art, the catalyst, the preparation method thereof and the application thereof have the advantages of simple method, convenient operation, high hydrothermal stability and high conversion rate, thereby further reducing energy consumption, saving resources and reducing production cost.