To obtain the degradation ruler and mechanism of the solar cell containing distributed Bragg reflectors (DBR) at electron irradiation, Macleod software was used to design suitable DBR for upright metamorphic GaInP/Ga(In)As/Ge triple-junction solar cell, and 1 MeV electron irradiation experiment was carried out on the solar cell. Al last, the electrical properties degradation was analyzed by the method of mathematically fitting. The results show that the theoretical highest reflectance is basically consistent with the experimental value. With the increase of irradiation fluence, the electrical parameters deteriorate is seriously and the degradation rate of short-circuit current is larger than that of open-circuit voltage, the external quantum efficiency degradation of the solar cell in long wavelength is gradually serious, and the degradation rate of short-circuit current in the Ge sub-cell is larger than that of other sub-cells. With the increase of irradiation influnce,the maximum reflectance of the DBR gradually degrades in bandwidth area under the same irradiation condition, but the short-circuit current can still be improved when the irradiation fluence is less than 2×10 ¹⁵ e/cm ², showing that the DBR has positive effects on anti-irradiation.