Abstract: In this paper, two-dimensional finite-difference time-domain algorithm (2D FDTD) and conformal meshing technology are adopted. By comparing with the flat ground, the influence of complex topography and geomorphology on the electromagnetic field propagation in Kunming, Yunnan is firstly studied. Then we further analyze the possible influence of the complex topography of the area on the accuracy of lightning location by time of arrival (TOA) method. The results shows that: 1) Due to the preferential attenuation of high-frequency lightning signals by the complex mountains, the larger the mountain on the propagation path, the longer the wave risetime of the corresponding lightning electromagnetic field, that is, the signal arrival time may be delayed. For the selected area of Kunming, it can be seen that the delay time of the peak value of the pulse waveform is distributed within 4–5 μs. 2) According to the different definitions of the pulse signal arrival time, for the flat ground or the real surface considering complex terrain, the 10% peak arrival method has smaller delay time. According to the lightning location technique by TOA method, when the ground is flat, the positioning result of the 10% peak method basically coincides with the assumed lightning strike position. For the complex real ground, the positioning error of the 10% peak method is basically about 2000 m and the location errors are different for different propagation paths.