We propose a narrow-band birefringent filter and its application in wide color gamut. The birefringent filter consists of five phase retarders and two polarizers, and it has both narrow band and high transmittance. In the experiment, we fabricate the birefringent filter using quartz phase retarders and polarizers, and apply it in serval different displays. The color gamuts of displays are enhanced more than 30%NTSC (National Television System Committee), and the widest color gamuts that have been obtained are 126%NTSC in liquid crystal displays and 138%NTSC in organic light-emitting devices. Moreover, the deep blue light in spectrum of display can be reduced using the birefringent filter. The birefringent filter can be an efficient element to achieve wide color gamut display.