An oxide-based green emitting phosphor, SrAlSiO: Mn (SASO: Mn) deriving from the feldspar mineral model has been successfully synthesized by a facile solid-state reaction. Upon 450 nm blue-light excitation, brightness narrow-band green light peaking at 517 nm with a full-width at half-maximum (fwhm) of 26 nm can be obtained. Owing to the narrow band emission, the CIE chromaticity coordinates are (0.182, 0.745) and the color purity of SASO: Mn is determined to be 78.3%. Meanwhile, the internal quantum efficiency (IQE) of the representative sample can reach up to 45.6% under 450 nm. In addition, the phosphor exhibits an extremely thermal stability, i.e., the integrated emission intensity at 420 K still remains 92% of the initial value. Furthermore, w-LED device fabricated from optimized phosphor SASO: Mn (green), commercial phosphor KSF: Mn (red) and blue LED chip can cover 120% National Television System Committee standard (NTSC) value. All these results suggest that the Mn ion activated green emitting phosphor has great potential for wide gamut w-LEDs backlights.