Rainfall simulators are helpful tools used to study hydrologic and erosion processes. Rainfall simulations researches are very rare in the Middle East region. In this research, an artificial rainfall simulator system has been developed to apply a controlled amount and rate of rainfall on a test plot located in an arid basin in western Saudi Arabia.  The simulator is intended to investigate rainfall-runoff relationship, infiltration and soil moisture in the experimental plot. It consists of sprinklers, water reservoir, piping, flow meter, pump and valves. The simulator has 240 sprinklers mounted 25 cm apart on five 12-meter long pipes and it is carried out on a 1-meter height metallic frame. The sprinklers are selected from nine locally available sprinklers base on its performance in regard of range of rainfall intensity and values of uniformity coefficient of rainfall produced by the sprinklers network. The designed rainfall simulator cover a large area compared to areas covered by most of previously designed simulators and its cost was moderate since its constructed from locally available materials.