Mesoporous g-C3N4 consisting of hollow nanospheres (MCNHN) was prepared via a facile vapor-deposition method. It demonstrated an excellent visible-light photocatalytic H-2 evolution activity of 22.3 times greater than bulk g-C3N4. The special hollow nanosphere structure, increased specific surface area and modified crystalline enabled MCNHN to realize stronger light harvest and better photoinduced electron-hole separation, which leaded to highly improved photocatalytic performance. The proposed method and setup are easy to be established, and have the potential for preparing nanoscale g-C3N4 with other tailored nanostructures.