[Objective] To study pore characteristics of mesoporous alumina with half-generation poly-amidoamine dendrimers (PAMAM) as template. [Methods] Mesoporous spherical (-alumina granules were prepared by an oil-drop process from aluminum isopropoxide with PAMAM as template. Transmitting electronic-microscope, X-Radial diffraction, infrared optical spectrometer and nitrogen adsorption porosimetry were applied to measure the characteristic of mesoporous alumina. [Results] It was found that a sponge- or worm-like randomly three-dimensionally connected mesoporous network could be obtained. Its mean pore diameters varied from 2 to 6 nm and its specific surface areas reached to above 320 m2 ·g-1. [Conclusions] Pore size of mesoporous alumina was related with the number of PAMAM generation added. The lower of the number of PAMAM generation added, the smaller of the alumina pore size obtained. With the increasing of PAMAM generations, pore size was nearly equal to the molecular size of PAMAM.