A new antireflective silica film with closed mesopores was successfully prepared for the optical elements used in vacuum of a high-power laser system. The ordered cagelike mesopores were formed with the direction of surfactant F127 and then closed by long-chain fluoroalkylsilane. The grazing incident x-ray diffraction and grazing incident small-angle x-ray scattering results indicated that the mesopores in film constructed a body-center cubic structure. The films exhibited excellent transmittance as high as 99.98% on quartz substrate. After a 1-month antipollution test with polydimethylsiloxane in vacuum, the decrease of transmittance was small as 0.02%. This film had a high laser-induced damage threshold of above $28\mathrm{J}/{\mathrm{cm}}^2$ at 1 ns laser pulse of 1053 nm wavelength.