Abstract: Considering detection principle and terrain factors, the lightning electromagnetic field propagation mode of irregular ups and downs based on the theory of Barrick surface impedance and Wait approximate algorithm was used to analyze that complex terrain was influence on lightning electromagnetic wave transmission, which used two-dimensional surface model of 60 km combined with the real complex terrain surface data of Sichuan province. Taking the typical terrain of Wenjiang and Baiyu as an example, the results of analyses is that the minimum value of the extended increment of the lightning wave propagation path is only 182m on the low altitude area of eastern plains of Wenjiang and the corresponding time delay increment is 0.61μs. The path extension increment reaches a maximum value of 2290m and the corresponding time delay increment is 7.63μs because there are many plateaus and mountains on western of Wenjiang. The path extension increment is more than 3000m on Baiyu station of western plateau, which the minimum value is 3025m and the corresponding time delay increment is 10.1μs. The path lengthening increment reaches a maximum value of 8283m and the corresponding time delay increment is 27.6μs. It points out that the complex terrain caused by lightning electromagnetic wave propagation path increment and corresponding transmission time increment must be considered in actual lightning detection positioning in order to improve the lightning location precision and efficiency.