Plant growth is selective to the absorption of the solar spectrum. Plants in the process of photosynthesis and growth are more sensitive to blue-violet light and red light. This paper designed and fabricated an optical filter to filter out yellow and green light with minimal absorption rate of photosynthesis so as to collect blue-violet light and red light which are necessary for plant growth. The broadband negative filter was prepared on the K9 substrate with large size through electron-beam evaporation system and ion assisted deposition system. The transmittance was over 90% at 400~470 nm and 630~750 nm wavelength band, and the reflectance at 500~580 nm wavelength band was less than 0.2%. The test results show that the broadband negative filter meet the requirements of the plant cultivation.