Detailed analysis on the output characteristic and power influence factors of crystal silicon solar cell arrays and GaAs cell arrays have been done based on trough concentrating photovoltaic/thermal system. The results show that under concentrated light intensity, the output performance of GaAs cell array is better than crystal silicon solar cell arrays. Band-gap of solar cell arrays narrows and short circuit current increases very much in concentrated light intensity, which are good for output power. But open circuit voltage of cells drops a little for high recombination rate in depletion region produced by high light intensity, which has a restrictive effect to output power. At the same time the series resistance of cell arrays increases and working temperature of cell arrays rises which are brought about by high concentrated light intensity. In high concentrated light intensity, series resistance of cell arrays hugely affect the output power. When series resistance increases from 0 Ω to 1 Ω, the out put power of four cell arrays respectively drop by 6778%, 7493%, 7730% and 5801%.