Surface loading can cause certain deformations in subway tunnels, and excessive deformation will affect the safe operation of subway tunnels. To study the influence of asymmetric surface filling on variable-section subway tunnels, a finite element model of horseshoe-shaped and box-shaped tunnel structures was established based on the road backfilling reconstruction project above the side of a certain underground section of Shijiazhuang Metro. The surface settlement and tunnel stress-deformation patterns during road backfilling construction were analyzed and compared with field monitoring results for verification. Furthermore, the effects of parameters such as tunnel burial depth, loading magnitude, and loading dimensions on the underlying variable-section tunnel were discussed. The results show that: under asymmetric filling, the surface soil displacement field approximately exhibits a "V"-shaped settlement; the maximum surface settlements in the tunnel areas of horseshoe-shaped and box-shaped sections are 15.85 mm and 27.17 mm, respectively; tunnel structural deformation is dominated by vertical settlement with relatively small horizontal deformation; compared with the horseshoe-shaped section tunnel, the box-shaped section tunnel is more significantly affected by surface loading; the deformation of the tunnel at the intersection between the horseshoe-shaped and box-shaped sections shows a certain abrupt change, and cracking and water leakage issues in this junction area require close monitoring during construction; loading magnitude and loading range are positively correlated with tunnel vertical settlement, while the horizontal distance between the loading center and tunnel axis and tunnel burial depth are negatively correlated with tunnel vertical settlement; the loading range has a significant influence on the distribution range of tunnel settlement. When the tunnel burial depth exceeds 24 m or the horizontal distance between the loading centerline and tunnel axis exceeds 50 m, surface loading has almost no effect on tunnel settlement.