Nitrogen-doped carbon has been receiving tremendous research interest due to its exotic electrochemical performance and catalyzing capability. Nevertheless, large-scale synthesis of ordered, mesoporous, nitrogen-doped carbon for supercapacitors is rarely reported due to the complexity and uncontrollable property of polymerization of carbon/ nitrogen precursors. In this work, we report a facile and efficient approach for mass production of nitrogen-doped carbon, with a narrow pore size distribution and a sheet morphology, via a simple solution casting of biomass-based mixture. Upon drying, the gelatin molecules self-assemble into sheets, and guide the homogeneous loading of sacrificial silica nanospheres. Further carbonization and template removal procedures allow the low-cost production of nitrogendoped carbon sheets in the absence of complex polymerization. As a result, nitrogen-doped carbon sheets possess a high nitrogen content and ordered, interconnected mesoporous channels, with porosity parameters being carbonization temperature and template size dependence. Additionally, nitrogen-doped, ordered carbon sheets exhibit high performance for supercapacitor application, including high specific capacitances and energy/power densities. This work demonstrates a unique route to synthesizing ordered mesoporous nitrogen-doped carbon sheets via a scalable, low-cost method, which may shed light on many other applications aside from energy storage, such as water splitting, catalysis and sensor.