The dynamic evolutional characteristics of return stroke channel are of great significance for studying the micro-physical mechanism of the lightning discharge process. This paper established a simplified radiation-hydrodynamic model (RHM) of the return stroke channel radial expansion based on the fluid dynamics theory and the light radiation characteristics of the discharge process. The temporal evolutions of the return stroke channel were analyzed. The results indicated that the current peak value and the rising time are important factors affecting channel dynamics characteristics. Before the peak current, the channel temperature and pressure reached the maximum, which make the channel accelerate expand. After the peak current, the channel temperature could rise to another higher peak. The decline in temperature was far slower than that of the current. This work provides reference data for further research on the radial energy transport of return stroke channels and the formation mechanism of shock waves.The dynamic evolutional characteristics of return stroke channel are of great significance for studying the micro-physical mechanism of the lightning discharge process. This paper established a simplified radiation-hydrodynamic model (RHM) of the return stroke channel radial expansion based on the fluid dynamics theory and the light radiation characteristics of the discharge process. The temporal evolutions of the return stroke channel were analyzed. The results indicated that the current peak value and the rising time are important factors affecting channel dynamics characteristics. Before the peak current, the channel temperature and pressure reached the maximum, which make the channel accelerate expand. After the peak current, the channel temperature could rise to another higher peak. The decline in temperature was far slower than that of the current. This work provides reference data for further research on the radial energy transport of return stroke channels and the formation mechanism of shock waves.