The design and preparation of multi-band antireflection thin-film on barium fluoride optical elements is the key to improve the detection performance of photoelectric system. 1064 nm laser/long-wave infrared dual-band antireflection thin-film was designed and prepared on barium fluoride substrate. Based on the calculation method of the admittance in periodically symmetric structure thin-film system and the optimization algorithm of fitting periods and reference wavelength, study on the design method of the initial film system of the multi-band antireflection thin-film was carried out. The films were prepared using the thermal evaporation ion-assisted deposition method. The results show that the film has excellent optical properties with a transmittance of 94.0% at 1064 nm, average transmittance of 96.3% in the long-wave infrared spectral band from 8 to 12 μm, and transmittance of 99.4% at 8.2 μm. The laser/long-wave infrared dual-band antireflection thin-film can be applied to dual-mode composite photodetection optoelectronic equipment, which is of great significance to improve the working performance of the photodetection system.