The study primarily depends upon the climate data to analyze the climatic characteristics related to lightning activity, and the data collected by the lightning location finder is also required to denote the cloud to ground lightning density of each grid cell. According to its degree of exposure to lightning and the characteristics of lightning protection and avoidance, the potential lightning striking areas are classified as the building, the outdoor area under the building canopy and the open field area. The expected lightning stroke times (frequency) on each class of lightning striking area have been worked out properly with the parameters of CG flash density, equivalent intercepting area to lightning, lightning protecting capability and position factor in these areas. Eventually the risk assessment has been carried with the formula of risk = frequency×population. The assessment reveals that with dense population and aggregated belongings, the central urban district is the highest risk zoning of lightning, as well as its high flash density, while the risk of the suburbs and rural areas are not high. The conclusion is demonstrated by the distribution of lightning disaster event occurring in Beijing from 2004 to 2008, and the result of the risk assessment is correspondent to the actual trend and situation.