Based on the conventional ground observation data and ERA5 reanalysis data, the vertical structure and evolution mechanism of the low vortex during the heavy precipitation process in North China during July 19-21, 2016 (case 1) and July 11-13, 2021 (case 2) were compared and analyzed in this paper. The results show that the two vortex systems are generated in a similar circulation background of low west and high east, and the upper-level jet stream in case 1 is significantly stronger than that in case 2, which is the obvious difference between the two vortex structures in large-scale circulation background. The vertical structure of the two low vortices is different. In case 1, the low vortices develop deeply in the vertical direction, and there are two positive vorticity centers in the upper layer (300 hPa) and the lower layer (850 hPa), respectively. With the movement of the low vortex, the positive vorticity center in the lower layer gradually weakens, while the positive vorticity center in the upper layer gradually increases, and the temperature distribution is warm at the top and cold at the bottom. There is a weak warm core structure at 400 hPa, under which there is a cold air mass, and the dry and cold air on the west side of the central axis of the vortex. In case 2, the development of low vorticity is relatively shallow, with only one positive vorticity center in the lower layer, and it is always located at 850 hPa. The middle troposphere presents an obvious warm core structure between 700 and 300 hPa, and the cold core near the ground. The development of the two low vortex systems is related to the downward transmission of the upper potential vortex and the transport of warm and humid air at the lower level. However, in case 1, there is the intrusion of dry cold air, and there is obvious frontogenesis and convective instability in the upper and lower levels, which is conducive to the generation of upward motion and the enhancement of positive vorticity. In case 2, the whole troposphere is dominated by warm advection, and the center of the potential vortex and the center of the warm advection are both below 850 hPa, and they almost overlap, resulting in upward motion and the development of the low vortex system. The vorticity budget analysis reveals that during various evolution stages of the two vortices, the budget on the northern and eastern sides of the vortex centers is positive, indicating a tendency for the vortices to move eastward and northward. The horizontal divergence term and the tilting term play a primary positive role in the vorticity growth at the lower levels of the two North China vortices during their development stages. The advection term and the divergence term contribute significantly and positively during the strength and attenuation stages. The difference between the two cases lies in the fact that, for Case 1, the vertical term contributes positively in the strength and attenuation stages, particularly in the vortex center and its eastern side, whereas for Case 2, the vertical term remains negative throughout the entire evolution process.