Cloud-to-ground lightning activities have a very significant relationship with the regional topography and landform environment. When carrying out the construction of transmission lines and the design and transformation of lightning protection measures, it is necessary to fully understand the characteristics of CG lightning activities in the transmission line area. In this paper, two data analysis methods, mathematical statistics and data mining, are used to study the relationship between CG lightning activity and terrain in Yunnan Province. Through statistical analysis of the geomorphic parameters and the distribution of CG lightning activity parameters throughout Yunnan Province, the influence of different topographic factors on CG lightning activity is revealed. Aiming at studying the coupled effects of various topographic factors on CG lightning activities, the Apriori algorithm was used to mine terrain attribute sets that are strongly correlated with high flash density and strong lightning current amplitude, and summarized the terrain scenes that are prone to lightning strikes.