The fullerene structures of C20cage and bowl,C20H10 and their N-doped structures as C20cage NH,C20bowl NH, C20H10NH, C20H10N and their isomers are optimized using the MPW1PW91/6-31G level of the theory. Magnetic shielding tensors of 14N and 13C atoms are calculated by the same level of the theory. Results show that doping an N atom on fullerenes affects differently on the chemical shielding of C atoms which are connected to the N atom to be distinguishable experimentally. The maximum chemical shielding of N and N-connected C atoms were shown in the isomer of C20H10NH. It seems that this structure with maximum bond length of C-N is the suitable molecule for additional reactions.