The mesoporous materials with pore size expansion were synthesized by hydrothermal method with cetyltrimethylammonium bromide (CATB) as template. The N, N-dimethyl formamide (DMFA) amine was selected to expand the pore size of these materials. The samples were characterized by XRD, N2 adsorption and SEM. The pore size could be changed with post treatment temperature. The range of pore size was 3.94 - 5.83 nm. The pore size didn't increase with the increasing of post treatment temperature. The SEM pictures of materials with pore expansion by post-hydrothermal treatment clearly revealed that the resulting particles were almost perfectly spherical in shape. The XRD analysis showed the typical Bragg reflections of the hexagonal V-MCM-41 material by DMFA at 130 °C for 48 h in the post hydrothermal synthesis.