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Based on the cloud-to-ground(CG) data from 2000 to 2003 collected by the XDDO3A lightning detection system in Beijing,a study was made of the daily and monthly lightning variation,as well as lightning intensity,polarity and density,etc.,and the climatic characteristics of lightning in Beijing was analyzed.The results show that most cloud-to-ground flashes are negative;the mean intensities of positive CG flashes are bigger than those of the negatives;the CG flashes have a daily variation characteristic of two peaks and two valleys;the maximum number of lighting days was found in July and August(lightning occurs almost every day),and lightning occurs most frequently in August;and in Beijing,CG flashes occurred mostly in four areas,and the spatial distribution of lightning is related to the topography and the nature of the underlying surface.