Abstract. For experiments like HAGAR, based on atmospheric Cherenkov technique, performance of the experiment depends strongly on the level of night sky background (NSB) at the observation site. Proper modeling of NSB in simulations is important to get the realistic estimate of the performance parameters. Here we present the Monte Carlo simulation of NSB and its comparison with experimental data. Effect of after-pulsing in photo-multiplier tubes is also modeled in present simulations.