Based on the construction of municipal road in the soft soil layer in a city, through the mutual verification of the calculation results of the finite element numerical simulation method and Asaoka method, the final stable settlement of the typical section of the current pavement is predicted. Based on this, the influence of the schemes of using common subgrade filling materials and lightweight concrete materials to backfill the subgrade on the post construction settlement of the subgrade is discussed. Results indicate that the current pavement settlement is basically stable. If the lightweight concrete material is used to backfill, the post-construction settlement of the subgrade can effectively reduce, with reduction of 34.3%.