In this paper, influence of temperature and reverse bias on photocurrent spectrum and spectral response of a monolithic GaInP/GaAs double-junction solar cell was investigated in detail. Two sharp spectral response offsets, corresponding to the bandedge photo absorption of the bottom GaAs and the top GaInP subcells, respectively, show the starting response points of individual subcells. More interestingly, the cell photocurrent was found to enhance significantly with increasing the temperature. In addition, the cell photocurrent also increases obviously as the reverse bias voltage increases. The integrated photocurrent intensity of the top GaInP subcell was particularly addressed. A theoretical model was proposed to simulate the reverse bias dependence of the integrated photocurrent of the GaInP subcell at different temperatures.