The main purpose of this paper is to compare efficiency of the multi-layer solar cell GaAs (2,3,5layer). There are various design parameters such as material type, thickness of the layers, dopingconcentration, type of texturing, and thickness of anti-reflective coating on which efficiency of the multi-layer solar cell depends.one-dimensional solar cell simulation software PC1D (personal computer in one dimension) used for determined the performance of the solar cell. Batch mode of PC1D provide optimization study for a particular parameter. After simulation in PC1D, open circuit voltage, short circuit current, maximum rated power and power conversion efficiency under the one sun, AM1.5G solar radiation and constant intensity of 0.1w/cm2are obtain