Extreme rainstorm in Henan Province, China, from July 19 to July 21, 2021, was accompanied by a lot of low-level jet (LLJ) activity. The horizontal motion equation, the kinetic energy equation, and the geopotential height gradient equation in isobaric coordinate system are used in this research to investigate the key physical factors influencing the evolution of LLJ using ERA5 data. According to the investigation, the LLJ center initially formed at 925hPa near Zhengzhou, developed and intensified to the northwest vertically, and then its core location was elevated to 850hPa and 700hPa, successively. The horizontal gradient of the geopotential height had a significant impact on the local change of the zonal and meridian winds of the LLJ. The mountainous territory to the west of Zhengzhou had a low value system of geopotential height, while the plain region to the northeast of Zhengzhou had a geopotential height system with a high value. The two of them generated a strong zonal gradient force of geopotential height near Zhengzhou, which, in conjunction with the zonal east wind, driving the growth of kinetic energy of LLJ. The anomalous distribution of geopotential height was mostly attributable to surface geopotential height and the vertical integration of near-surface virtual temperature. The calculation of equation of the zonal gradient of geopotential height revealed that the vertical advection of potential temperature resulting from the zonal gradient of vertical velocity and the zonal gradient of diabatic heating were the principal forcing terms for the local variation of the zonal gradient of geopotential height. The relatively low temperature region in the mountainous region and the relatively high temperature region in the plain region had a significant effect on the development and evolution of the LLJ.