Lightning strikes are the primary factor causing tripping of overhead transmission lines, and analysis of thunderstorm activity trajectories can provide guidance for differentiated lightning protection of transmission lines. This paper proposes research method for the analysis of cloud-to-ground lightning based on clustering algorithm, which is used to evaluate the ground flash process of a transmission lines where lightning strikes tripped frequently. In order to describe the spatial and temporal evolution of cloud-to-ground activity; OPTICS algorithm is used to determine structure of cloud-to-ground lightning, based on which the parametric expression cloud-to-ground lightning of is carried out, and to study changes of cloud-to-ground lightning parameters with the topography. The results show that the frequency of cloud-to-ground lightning tends to decrease as the ground flash activity develops towards high-altitude regions.