An innovative scheme of lightning pulse source for the FDTD is developed to simulate a segment of lightning and its electromagnetic field in near field region. A filament of current is set up using FDTD to imitate a segment of lightning channel. The filamentary current is extended into the PML, reaching the metal boundary outside the PML, which forms a loop. This method avoids the charge effect at the top and end of the filamentary current. It is found that this method could simulate the lightning electromagnetic field accurately, compared with the analytic function of classical lightning electromagnetic field in free space. And then the lightning pulse field engendered by this method is used to analyse the interaction with a carbon fibre cabin in airplane and its inner electric field.