The nuclei around magic number N=126 are investigated in the deformed relativistic mean field (RMF)model with effective interactions TMA.We focus investigations on the N=126 isotonic chain.The N=126 shellevolution is studied by analyzing the variations of two-neutron (proton) separation energies,quadruple deformations,single particle levels etc.The good agreement of two-neutron separation energies between experimental data and calculatedvalues is reached.The RMF theory predicts that the sizes of N=126 shell become smaller and smaller withthe increasing of proton number Z.However,the N=126 shell exists in our calculated region all along.According tothe calculated two-proton separation energies,the RMF theory suggests ~(220)Pu is a two-proton drip-line nucleus in theN=126 isotonic chain. The nuclei around magic number N = 126 are investigated in the deformed relativistic mean field (RMF) model with effective interactions TMA. We focus investigations on the N = 126 isotonic chain. N = 126 shellevolution is studied by analyzing the variations of two- neutron (proton) separation energies, quadruple deformations, single particle levels etc. The good agreement of two-neutron separation energies between experimental data and calculated values ​​is reached. The RMF theory predicts that the sizes of N = 126 shells become smaller and smaller withthe increasing of proton number Z. However, the N = 126 shell exists in our calculated region all along. According to calculated two-proton separation energies, the RMF theory suggests ~ (220) Pu is a two-proton drip- 126 isotonic chain.