Abstract: In this paper, the damage characteristics were determined firstly by measuring the spectral responses of triple-junction(TJ) GaInP2/GaAs/Ge solar cells. Then the electrical properties of the TJ cells were determined as a function of the fluences under the irradiation of various charged particles, and the equivalent coefficients related to the irradiated displacement- damage were determined. Based on these results, an evolution law of the mass output power was established as a function of the displacement damage dose of the TJ solar cells under the charged particle irradiation. Finally, the displacement damage dose of the TJ solar cells served in GEO was calculated, from which the orbital behaviors of the TJ solar cell could be evaluated.