Narrowband filters with central wavelength 1064 nm are key optical elements used in the large scale solid state laser facility. In order to fabricate a filter with large size and high precision, the influence of monitoring wavelength on signal noise ratio and stability is investigated. Moreover, the monitoring strategy is optimized to satisfy the precision need for fabricating a narrowband filter. Film spectra analysis in fabrication process indicates that the actual thickness of HfO₂ will smaller than design value gradually, and the actual thickness of SiO₂ will greater than design value gradually, with the proceed of coating. The thickness error as a result of the different variation tendency for HfO₂ and SiO₂ in the evaporation process, and the mask plate induced error are key points of affecting the bandpass property. One 200 mm × 200 mm size narrowband filter with 5 nm full width at half maximum (FWHM) and over 19.5 J/cm² (3 ns) laser damage threshold at 1064 nm is successfully fabricated.