According to the requirement of ultraviolet (UV) warning system, based on the structure of Fabry-Perot (F-P) narrowband filter, by analysing film systems theory, the research of material evaporation process, adjustment and optimization of the ion source parameters, using the combination of different film system design, the UV filter film which can collect the UV signal effectively is designed and prepared. The peak transmittance of this film in UV is 17.96%, half-peak bandwidth is 20 nm. The filter can collect the UV signal more accurate and ultraviolet and visible band are inhibited effectively, so the background noise can be controlled at a low level. The cut-off degree is less than -30 dB. This film can filter natural light and collect the UV signal effectively in the UV warning system, and it has a significant contribution to improve the overall accuracy of the system.