This paper describes a power quality analysis of a photovoltaic generating systems. Prior to the power measurement, domestic and foreign codes related to the photovoltaic generating systems were briefly summarized. After constructing about 5 kW photovoltaic systems, input/output voltages and currents were measured to compare and analyze the power quality by the module type. Based on the measured values, a couple of factors such as active power, power factor, total harmonic distortion(THD) was calculated and analyzed.