In order to evaluate the effect of irradiation on the spectral properties of Cr:MgAl2O4 crystal, Raman spectra, transmittance spectra and fluorescence properties of the polished Cr:MgAl2O4 crystal were measured before and after γ irradiation with a dose of 100 Mrad, and the mechanism of the irradiation effect were analyzed. The results show that the position and intensity of Raman vibration peak are both affected by irradiation, but the number of vibration peaks does not change. And due to the absorption of color center, the transmittance in the wavelength range of 250-600 nm decreases obviously after γ irradiation. The fluorescence emission peaks of the samples after irradiation are consistent with those of before irradiation, while the fluorescence emission intensity decreases significantly and the fluorescence lifetime increases significantly after irradiation.