Abstract: The modeling of electromagnetic field radiation characteristics of lightning channel has always been a key issue in the lightning protection technology development and lightning science research. Ideal and simple vertical channels are often used for modeling, various analytical and numerical methods are adopted to get more effective results. However, there are few researches on fine channel structures such as branched channels, so the fields obtained by vertical models may deviate from the actual measured fields. In this paper, based on the equation of moving charged particles (MCP), the return electromagnetic field of lightning branch channel is calculated, and the components of radiation field, velocity field and electrostatic field and the total field are calculated respectively. The results show that the existence of branch channel leads to the appearance of subpeak, and the waveform is related to the observation point position, the speed of return stroke, the height of bifurcation point and other parameters. The change of velocity vector of MCP is just in line with this characteristic and can better reflect the physical characteristics in the process of return stroke. Compared with dipole solution method, this method avoids the differential operation of return current, and is an efficient method to analyze the radiation field of lightning channel.