Abstract: Antireflective microstructure (ARMS) is an important method to improve the transmittance of optical windows. A design and fabrication method of ARMS on fused silica glass windows was introduced. A moth-eye microstructure model was designed. Using the finite-difference time-domain (FDTD) method, the characteristic parameters such as period, depth, and duty cycle of ARMS were controlled, and the theoretical average transmittance could exceed 96%. The fabrication of ARMS was realized by laser interference lithography mask preparation and inductively coupled plasma (ICP) etching of micro/nano structures. The microscopic morphology of ARMS was observed by scanning electron microscope (SEM). The fabricated ARMS have a feature size of less than 200 nm and a duty cycle greater than 0.6. Finally, a comparison of transmittance with optical windows of different surface states shows that the designed and fabricated ARMS can effectively improve the optical transmittance of quartz glass optical windows in the 450 nm ~1500 nm band.