Herein, we prepare three-dimensional B-doped N-containing carbon foams with a mesoporous structure by annealing boric acid-impregnated commercial melamine foam and characterize the obtained samples by a range of instrumental techniques. The chemical composition, structure, and electrochemical performance of B-doped N-containing carbon foams are shown to be dependent on annealing temperature (500-900 degrees C), e.g., increasing the annealing temperature from 500 to 700 degrees C results in the formation of a mesoporous structure and promotes B doping, which increases the concentration of carriers, the rate of ion transport and electrical conductivity. However, a further increase of annealing temperature from 700 to 900 degrees C leads to the collapse of pore structure and the formation of insulating boron nitride, causing electrochemical performance deterioration. As a result, optimal performance is observed for samples annealed at 700 degrees C (capacity = 462 mF cm(-2) at a current density of 0.2 mA cm(-2)). More importantly, the supercapacitor has an obvious improvement in the rate capability. The successful fabrication of B-doped N-containing carbon foams and in-depth study of the electrochemical performance highlights the importance of tuning the concentration of doped heteroatoms, pore structure, and electrical conductivity for the design of carbon-based supercapacitors.