The present invention relates to a method for preparing nanoporous carbons with enhanced mechanical strength and the nanoporous carbons prepared by the method, and more specifically, to a method for preparing a nanoporous carbon, comprising the steps of (i) synthesizing a mesoporous silica template not being subjected to any calcination process; (ii) incorporating a mixture of a monomer for addition polymerization and initiator, or a mixture of a monomer for condensation polymerization and acid catalyst into the as-synthesized mesoporous silica template, and reacting the mixture to obtain a polymer-silica composite; and (iii) carbonizing the polymer-silica composite at a high temperature to obtain a carbon-silica composite, from which the silica template is then removed using a solvent.According to the preparation method of the present invention, the nanoporous carbons having uniform size of mesopores, high surface area and high mechanical stability can be prepared at low preparation cost through a simplified preparation process. Therefore, the nanoporous carbons of the present invention can be used as catalysts, catalyst supports, separating agents, hydrogen reserving materials, adsorbents, membranes and membrane fillers in various application fields.