The relation of annual thunderstorm days and annual mean lightning density is researched by statistical analysis in different radius areas from the meteorological stations, based on the cloud ground lightning data detected by the Hubei ADTD lightning position determination and monitoring system from 2007 to 2010 and the thunderstorm days of the 28 meteorological stations where lightning monitoring detection efficiency is above 95%. The results have indicated that, in the 18-20 km radius region, the correlation coefficient is obviously increased. When the radius is 18 km, the correlation coefficient reaches a maximum value of 0.8521. Thus we can consider that generally observers only can hear thunderclap in the 18-20 km radius region. The relations of annual thunderstorm days and annual mean lightning density is formulated by statistical fitting: NG=0.029Td1.5, and this equation even surpasses the standard equation (Ng=0.024Td1.3) obviously through the verification of the data in 2011.