In the power grid, Power distribution lines are usually exposed in the air and vulnerable to power supply interruption caused by lightning induced overvoltage.About the spatial distribution characteristics of coupling overvoltage of the transmission line, the FDTD is used to simulate the Lightning Induced Overvoltage on the location of the lightning point relative to the middle point and the end point of the distribution line, and the peak time and the spatial trend of the overvoltage are studied. The research shows that when lightning strikes onthe middle part of grid line, the peak value of the overvoltage is 28.07kV. The induced charge of the neutral point at the middle of the line is the largest, and the bound electric charge at the midpoint position moves rapidly to the two ends. The over voltage peak of the lightning stroke relative to the end point of the line is 32.74kV.