Abstract: A kind of quadruple-junction GaAs solar array (IMM quadruple-junction array) is proposed and tested. The bandwidths of the semi-conductive materials used in the array are 1.9, 1.4, 1.0, and 0.7 eV, respectively. The photoelectric conversion efficiency of the IMM quadruple-junction array can be greatly improved as compared with the three-junction gallium arsenide solar arrays. The matching between four P-N junctions and the AM0 solar spectra is ameliorated due to the specific physical characteristics of the material. The structure and the process design of the battery are presented with the aim to improve the photovoltaic efficiency. The typical electrical performance data of the solar array are acquired via the telemetric system. It is shown that the performance of the IMM quadruple-junction array, as featured by the open-circuit voltage of 3.321V, the short-circuit current density of 15.76 mA/cm², and the practical photovoltaic efficiency ranging between 34.44% and 34.79%, is much better than that of the conventional three-junction array.