The laser induced infrared fluorescence spectra of the crystal Cr:Mg_2SiO_4 at room temperature and liquid-nitrogen temperature with the wavelength of inducing laser being 1064and 532nm, respectively, are reported. The characteristics of the infrared fluorescence spectra are described and analyzed. On the assumption which is verified by theoretical calculations that the complex ions (CrO_6)~(9-)and (CrO_4)~(4-)simultaneously exist in the crystal Cr:Mg_2SiO_4, the interpretation of infrared fluorescence spectra is discussed.