Abstract: Based on the ADTD system lightning location data from 2007 to 2017 in Guangxi, the differences of cloud to ground flashes (CG) between the pre and post flood season were analyzed. In addition, the causing factors were discussed. The results are as follows. (1) During the pre and post flood season, the diurnal variation and spatial distribution of CG frequency were obviously different and the spatial distribution of the average lightning current amplitude was relatively consistent. (2) There were mainly negative CG flashes in the whole flood season, and the positive CG flashes were more likely to occur in the pre flood and relatively rare in the post season. The average amplitude of positive lightning current was larger than that of negative lightning current, and the average lightning current amplitude in the post flood season was larger than that in the pre flood season. (3) The intensity and onset time of SCS summer monsoon had great influence on the lightning activities in the pre flood season. Lower lightning intensity was accompanied by earlier occurrence and less CG flashes and vice versa. In the pre flood season, the high value area of CG flashes was greatly influenced by frequent interactions of large-scale cold and warm air flow under the guidance of topography. In the post flood season, the afternoon solar radiation, the uplift of the special topography and the tropical system weather had a great influence.