Here we report a new approach referred as "soft-to-hard templating" strategy via the copolymerization of carbon source (dopamine) and silica source (tetraethyl orthosilicate) for the synthesis of well dispersed N-doped mesoporous carbon nanospheres (MCNs), which exhibit high performance for electrochemical supercapacitor. This method overcomes the shortcoming of uncontrolled dispersity and complicated procedures of soft- or hard-templating methods, respectively. Moreover, the synthesized MCNs feature enriched heteroatom N-doping and easy functionalization by noble-metal nanoparticles during the one-pot synthesis. All the above characters make the as-prepared MCNs a promising platform in a variety of applications. To demonstrate the applicability of the synthesized nitrogen-doped MCNs, this material has been employed as an electrode for high-performance electrochemical supercapacitor, which shows a capacitance of 223 and 140 F/g at current densities of 0.5 and 10 A/g in 1 mol/L KOH electrolyte, respectively.