In order to reduce the harmful blue light component of LEDs and other illumination modalities to human eyes, we propose a reduced harmful blue light attenuator based on the local surface plasmon resonance effect of self-assembled metal nanoparticles. The silver-covered gold nanoparticles (Au@Ag NPs) and silver nanoparticles (Ag NPs) were prepared by synthesis. Nanoparticle monolayers film were prepared on quartz glass using the self-assembly method, and the particle morphology film and distribution were changed by post-treatment through annealing. The scanning electron microscopy (SEM) images were used to analyze the morphology of nanoparticles of different samples as well as the arrangement pattern. The samples were subjected to UV-Vis transmission spectroscopy and the transmission was simulated with the help of time-domain finite difference method to analyze the factors affecting the transmission peaks. The results show that the samples prepared by the self-assembly method have selective attenuation of light transmission at different wavelengths and the attenuation peaks are blue-shifted after annealing. Finally, this paper shows the actual light transmission effects of different samples under white LEDs, in which the annealed Ag NPs sample can reduce the transmission to 24.5% at the 416 nm harmful blue light band, which significantly and effectively attenuates the harmful blue light and has excellent blue light protection effect.