Spherical nitrogen-doped porous carbons have been prepared through a template carbonization method, in which polyacrylamide (PAM) serves as carbon and nitrogen sources, and calcium acetate as hard template. It reveals that the mass ratio of polyacrylamide and calcium acetate and the carbonization temperature have crucial impacts upon the pore structures and the correlative capacitive performance. The PAM-Ca-650-1:3 sample displays the best capacitance performance. It is amorphous with low-graphitization degree, possessing a total BET surface area of 648 m(2) g(-1) and total pore volume of 0.59 cm(3) g(-1). At a current density of 0.5 A g(-1), the resultant specific capacitance is 194.7 F g(-1). It exhibits high capacitance retention of 97.8% after charging-discharging 5000 times. The polyacrylamide used is cheap and commercially available, making it promising for large-scale production of porous carbons containing nitrogen as an excellent electrode material for supercapacitor.