This paper presents the GUI design of the photovoltaic array monitoring system. The system monitor solar irradiance, temperature, short-circuit current, open-circuit voltage, maximum power, voltage and current at maximum power, fill factor and also efficiency of PV array. It was designed on ATmega8535 microcontroller. The GUI display the graph and the data can be saved Microsoft excel format. The calibration of sensors feature is included in GUI. The GUI was developed using VB.Net.