This paper introduces the distribution of karst in Guangdong and the basic situation of geological disasters of karst collapse. By analyzing and studying the disaster cases of karst collapse which have occurred in Guangdong in recent years, the various induced factors of karst collapse are also theoretically analyzed, such as hydrological factors, surface water erosion, reservoir impounding, groundwater pumping, vibration effect, load function. Then, two main genetic mechanisms of karst land collapse: suffusion theory and vacuum erosion theory are discussed. Through field investigation and references of previous research results, it shows that the karst land collapse has been formed based on the suffusion theory in most areas of Guangdong. Based on the above analysis and the characteristics of power grid system, the evaluation method of transmission lines in karst collapse areas is proposed. Moreover, the stability of transmission tower in collapse areas by using numerical simulation method is investigated to get the results in accordance with the reality, which proves that the method could be promoted.