Abstract: Based on the requirements of glued eyepiece for the optical filter in the observation scope system, a cut-off filter for the optical system of the scope was designed, which eliminated the half-wave hole of the filter and compressed the passband ripple. The optical filter was prepared by electron beam thermal evaporation technology and its transmittance was tested. The average transmittance in the range of 400 nm~630 nm is 95.76%, and the average transmittance in the range of 655 nm~800 nm is 0.06%. The sample passes the salt spray test and the mechanical firmness test, and the preparation results meet the design requirements.