When using vacuum preloading technology to treat soft soil foundations around existing roads，we should consider the influence of vacuum preloading construction on existing roadbed and ensure the safe operation of existing roads. Taking an actual project as an example，this paper summarizes and corrects the empirical formula through similar projects，and the calculation results reveal that the existing road is within the influence range of vacuum preloading. To ensure the safe operation of Dongdi Road and the effect of foundation treatment，we set a protection zone with a width of 15 m on the side of the existing road near the vacuum preloading treatment area，use long and short plates with the length of the plastic drainage plate reduced from 8.0 m to 3.0 m from the side far of the road to Dongdi Road，and adopt the stacking preloading method with the stacking height of 3.0 m. For the protection of Dongdi Road，we monitor the horizontal and vertical displacement and settlement during the construction period. Finally，under the double guarantee of the earlier scheme design and monitoring during the construction period，the foundation treatment construction has been smoothly completed.