All Samples of alkaline-earth silicon oxynitride glasses were synthesized by conventional high-temperature melting reaction. The infrared spectra of all glasses were studied. The results show that the band between 800 and 1300 cm-1 becomes wider and loss intensity with increasing N content. With the same starting N content, glasses prepared of different alkaline-earth oxides show different infrared spectra. The absorption bands of CaO-SiO2-Si3N4, BaO-SiO2-Si3N4 glasses are wider than SrO-SiO2-Si3N4 glass.